2019-05-19 15:08:55 +03:00
// SPDX-License-Identifier: GPL-2.0-only
2005-04-17 02:20:36 +04:00
/*
* linux / fs / exec . c
*
* Copyright ( C ) 1991 , 1992 Linus Torvalds
*/
/*
* # ! - checking implemented by tytso .
*/
/*
* Demand - loading implemented 01.12 .91 - no need to read anything but
* the header into memory . The inode of the executable is put into
* " current->executable " , and page faults do the actual loading . Clean .
*
* Once more I can proudly say that linux stood up to being changed : it
* was less than 2 hours work to get demand - loading completely implemented .
*
* Demand loading changed July 1993 by Eric Youngdale . Use mmap instead ,
* current - > executable is only used by the procfs . This allows a dispatch
* table to check for several different types of binary formats . We keep
* trying until we recognize the file or we run out of supported binary
2016-12-21 08:26:24 +03:00
* formats .
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*/
# include <linux/slab.h>
# include <linux/file.h>
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# include <linux/fdtable.h>
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# include <linux/mm.h>
mm: per-thread vma caching
This patch is a continuation of efforts trying to optimize find_vma(),
avoiding potentially expensive rbtree walks to locate a vma upon faults.
The original approach (https://lkml.org/lkml/2013/11/1/410), where the
largest vma was also cached, ended up being too specific and random,
thus further comparison with other approaches were needed. There are
two things to consider when dealing with this, the cache hit rate and
the latency of find_vma(). Improving the hit-rate does not necessarily
translate in finding the vma any faster, as the overhead of any fancy
caching schemes can be too high to consider.
We currently cache the last used vma for the whole address space, which
provides a nice optimization, reducing the total cycles in find_vma() by
up to 250%, for workloads with good locality. On the other hand, this
simple scheme is pretty much useless for workloads with poor locality.
Analyzing ebizzy runs shows that, no matter how many threads are
running, the mmap_cache hit rate is less than 2%, and in many situations
below 1%.
The proposed approach is to replace this scheme with a small per-thread
cache, maximizing hit rates at a very low maintenance cost.
Invalidations are performed by simply bumping up a 32-bit sequence
number. The only expensive operation is in the rare case of a seq
number overflow, where all caches that share the same address space are
flushed. Upon a miss, the proposed replacement policy is based on the
page number that contains the virtual address in question. Concretely,
the following results are seen on an 80 core, 8 socket x86-64 box:
1) System bootup: Most programs are single threaded, so the per-thread
scheme does improve ~50% hit rate by just adding a few more slots to
the cache.
+----------------+----------+------------------+
| caching scheme | hit-rate | cycles (billion) |
+----------------+----------+------------------+
| baseline | 50.61% | 19.90 |
| patched | 73.45% | 13.58 |
+----------------+----------+------------------+
2) Kernel build: This one is already pretty good with the current
approach as we're dealing with good locality.
+----------------+----------+------------------+
| caching scheme | hit-rate | cycles (billion) |
+----------------+----------+------------------+
| baseline | 75.28% | 11.03 |
| patched | 88.09% | 9.31 |
+----------------+----------+------------------+
3) Oracle 11g Data Mining (4k pages): Similar to the kernel build workload.
+----------------+----------+------------------+
| caching scheme | hit-rate | cycles (billion) |
+----------------+----------+------------------+
| baseline | 70.66% | 17.14 |
| patched | 91.15% | 12.57 |
+----------------+----------+------------------+
4) Ebizzy: There's a fair amount of variation from run to run, but this
approach always shows nearly perfect hit rates, while baseline is just
about non-existent. The amounts of cycles can fluctuate between
anywhere from ~60 to ~116 for the baseline scheme, but this approach
reduces it considerably. For instance, with 80 threads:
+----------------+----------+------------------+
| caching scheme | hit-rate | cycles (billion) |
+----------------+----------+------------------+
| baseline | 1.06% | 91.54 |
| patched | 99.97% | 14.18 |
+----------------+----------+------------------+
[akpm@linux-foundation.org: fix nommu build, per Davidlohr]
[akpm@linux-foundation.org: document vmacache_valid() logic]
[akpm@linux-foundation.org: attempt to untangle header files]
[akpm@linux-foundation.org: add vmacache_find() BUG_ON]
[hughd@google.com: add vmacache_valid_mm() (from Oleg)]
[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: adjust and enhance comments]
Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Michel Lespinasse <walken@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Tested-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-04-08 02:37:25 +04:00
# include <linux/vmacache.h>
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# include <linux/stat.h>
# include <linux/fcntl.h>
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# include <linux/swap.h>
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# include <linux/string.h>
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# include <linux/init.h>
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# include <linux/sched/mm.h>
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# include <linux/sched/coredump.h>
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# include <linux/sched/signal.h>
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# include <linux/sched/numa_balancing.h>
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# include <linux/sched/task.h>
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# include <linux/pagemap.h>
perf: Do the big rename: Performance Counters -> Performance Events
Bye-bye Performance Counters, welcome Performance Events!
In the past few months the perfcounters subsystem has grown out its
initial role of counting hardware events, and has become (and is
becoming) a much broader generic event enumeration, reporting, logging,
monitoring, analysis facility.
Naming its core object 'perf_counter' and naming the subsystem
'perfcounters' has become more and more of a misnomer. With pending
code like hw-breakpoints support the 'counter' name is less and
less appropriate.
All in one, we've decided to rename the subsystem to 'performance
events' and to propagate this rename through all fields, variables
and API names. (in an ABI compatible fashion)
The word 'event' is also a bit shorter than 'counter' - which makes
it slightly more convenient to write/handle as well.
Thanks goes to Stephane Eranian who first observed this misnomer and
suggested a rename.
User-space tooling and ABI compatibility is not affected - this patch
should be function-invariant. (Also, defconfigs were not touched to
keep the size down.)
This patch has been generated via the following script:
FILES=$(find * -type f | grep -vE 'oprofile|[^K]config')
sed -i \
-e 's/PERF_EVENT_/PERF_RECORD_/g' \
-e 's/PERF_COUNTER/PERF_EVENT/g' \
-e 's/perf_counter/perf_event/g' \
-e 's/nb_counters/nb_events/g' \
-e 's/swcounter/swevent/g' \
-e 's/tpcounter_event/tp_event/g' \
$FILES
for N in $(find . -name perf_counter.[ch]); do
M=$(echo $N | sed 's/perf_counter/perf_event/g')
mv $N $M
done
FILES=$(find . -name perf_event.*)
sed -i \
-e 's/COUNTER_MASK/REG_MASK/g' \
-e 's/COUNTER/EVENT/g' \
-e 's/\<event\>/event_id/g' \
-e 's/counter/event/g' \
-e 's/Counter/Event/g' \
$FILES
... to keep it as correct as possible. This script can also be
used by anyone who has pending perfcounters patches - it converts
a Linux kernel tree over to the new naming. We tried to time this
change to the point in time where the amount of pending patches
is the smallest: the end of the merge window.
Namespace clashes were fixed up in a preparatory patch - and some
stylistic fallout will be fixed up in a subsequent patch.
( NOTE: 'counters' are still the proper terminology when we deal
with hardware registers - and these sed scripts are a bit
over-eager in renaming them. I've undone some of that, but
in case there's something left where 'counter' would be
better than 'event' we can undo that on an individual basis
instead of touching an otherwise nicely automated patch. )
Suggested-by: Stephane Eranian <eranian@google.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Paul Mackerras <paulus@samba.org>
Reviewed-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: <linux-arch@vger.kernel.org>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-21 14:02:48 +04:00
# include <linux/perf_event.h>
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# include <linux/highmem.h>
# include <linux/spinlock.h>
# include <linux/key.h>
# include <linux/personality.h>
# include <linux/binfmts.h>
# include <linux/utsname.h>
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# include <linux/pid_namespace.h>
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# include <linux/module.h>
# include <linux/namei.h>
# include <linux/mount.h>
# include <linux/security.h>
# include <linux/syscalls.h>
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# include <linux/tsacct_kern.h>
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# include <linux/cn_proc.h>
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# include <linux/audit.h>
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# include <linux/tracehook.h>
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# include <linux/kmod.h>
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# include <linux/fsnotify.h>
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# include <linux/fs_struct.h>
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# include <linux/pipe_fs_i.h>
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# include <linux/oom.h>
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# include <linux/compat.h>
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# include <linux/vmalloc.h>
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# include <linux/uaccess.h>
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# include <asm/mmu_context.h>
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# include <asm/tlb.h>
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# include <trace/events/task.h>
CRED: Make execve() take advantage of copy-on-write credentials
Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.
I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).
The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.
(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.
This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.
(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.
(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.
(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.
This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.
(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.
(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:
(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().
(ii) Clear any bits in current->personality that were deferred from
(c.i).
(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:
(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.
This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).
(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.
(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.
(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.
(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.
(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.
(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()
Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().
(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.
(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()
New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.
The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.
(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 02:39:24 +03:00
# include "internal.h"
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2012-02-07 20:11:05 +04:00
# include <trace/events/sched.h>
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int suid_dumpable = 0 ;
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static LIST_HEAD ( formats ) ;
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static DEFINE_RWLOCK ( binfmt_lock ) ;
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void __register_binfmt ( struct linux_binfmt * fmt , int insert )
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{
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BUG_ON ( ! fmt ) ;
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if ( WARN_ON ( ! fmt - > load_binary ) )
return ;
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write_lock ( & binfmt_lock ) ;
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insert ? list_add ( & fmt - > lh , & formats ) :
list_add_tail ( & fmt - > lh , & formats ) ;
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write_unlock ( & binfmt_lock ) ;
}
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EXPORT_SYMBOL ( __register_binfmt ) ;
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void unregister_binfmt ( struct linux_binfmt * fmt )
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{
write_lock ( & binfmt_lock ) ;
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list_del ( & fmt - > lh ) ;
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write_unlock ( & binfmt_lock ) ;
}
EXPORT_SYMBOL ( unregister_binfmt ) ;
static inline void put_binfmt ( struct linux_binfmt * fmt )
{
module_put ( fmt - > module ) ;
}
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bool path_noexec ( const struct path * path )
{
return ( path - > mnt - > mnt_flags & MNT_NOEXEC ) | |
( path - > mnt - > mnt_sb - > s_iflags & SB_I_NOEXEC ) ;
}
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# ifdef CONFIG_USELIB
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/*
* Note that a shared library must be both readable and executable due to
* security reasons .
*
* Also note that we take the address to load from from the file itself .
*/
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SYSCALL_DEFINE1 ( uselib , const char __user * , library )
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{
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struct linux_binfmt * fmt ;
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struct file * file ;
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struct filename * tmp = getname ( library ) ;
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int error = PTR_ERR ( tmp ) ;
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static const struct open_flags uselib_flags = {
. open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC ,
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. acc_mode = MAY_READ | MAY_EXEC ,
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. intent = LOOKUP_OPEN ,
. lookup_flags = LOOKUP_FOLLOW ,
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} ;
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if ( IS_ERR ( tmp ) )
goto out ;
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file = do_filp_open ( AT_FDCWD , tmp , & uselib_flags ) ;
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putname ( tmp ) ;
error = PTR_ERR ( file ) ;
if ( IS_ERR ( file ) )
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goto out ;
error = - EINVAL ;
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if ( ! S_ISREG ( file_inode ( file ) - > i_mode ) )
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goto exit ;
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error = - EACCES ;
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if ( path_noexec ( & file - > f_path ) )
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goto exit ;
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fsnotify_open ( file ) ;
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error = - ENOEXEC ;
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read_lock ( & binfmt_lock ) ;
list_for_each_entry ( fmt , & formats , lh ) {
if ( ! fmt - > load_shlib )
continue ;
if ( ! try_module_get ( fmt - > module ) )
continue ;
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read_unlock ( & binfmt_lock ) ;
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error = fmt - > load_shlib ( file ) ;
read_lock ( & binfmt_lock ) ;
put_binfmt ( fmt ) ;
if ( error ! = - ENOEXEC )
break ;
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}
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read_unlock ( & binfmt_lock ) ;
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exit :
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fput ( file ) ;
out :
return error ;
}
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# endif /* #ifdef CONFIG_USELIB */
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# ifdef CONFIG_MMU
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/*
* The nascent bprm - > mm is not visible until exec_mmap ( ) but it can
* use a lot of memory , account these pages in current - > mm temporary
* for oom_badness ( ) - > get_mm_rss ( ) . Once exec succeeds or fails , we
* change the counter back via acct_arg_size ( 0 ) .
*/
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static void acct_arg_size ( struct linux_binprm * bprm , unsigned long pages )
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{
struct mm_struct * mm = current - > mm ;
long diff = ( long ) ( pages - bprm - > vma_pages ) ;
if ( ! mm | | ! diff )
return ;
bprm - > vma_pages = pages ;
add_mm_counter ( mm , MM_ANONPAGES , diff ) ;
}
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static struct page * get_arg_page ( struct linux_binprm * bprm , unsigned long pos ,
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int write )
{
struct page * page ;
int ret ;
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unsigned int gup_flags = FOLL_FORCE ;
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# ifdef CONFIG_STACK_GROWSUP
if ( write ) {
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ret = expand_downwards ( bprm - > vma , pos ) ;
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if ( ret < 0 )
return NULL ;
}
# endif
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if ( write )
gup_flags | = FOLL_WRITE ;
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/*
* We are doing an exec ( ) . ' current ' is the process
* doing the exec and bprm - > mm is the new process ' s mm .
*/
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ret = get_user_pages_remote ( current , bprm - > mm , pos , 1 , gup_flags ,
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& page , NULL , NULL ) ;
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if ( ret < = 0 )
return NULL ;
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if ( write )
acct_arg_size ( bprm , vma_pages ( bprm - > vma ) ) ;
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return page ;
}
static void put_arg_page ( struct page * page )
{
put_page ( page ) ;
}
static void free_arg_pages ( struct linux_binprm * bprm )
{
}
static void flush_arg_page ( struct linux_binprm * bprm , unsigned long pos ,
struct page * page )
{
flush_cache_page ( bprm - > vma , pos , page_to_pfn ( page ) ) ;
}
static int __bprm_mm_init ( struct linux_binprm * bprm )
{
2009-01-07 01:40:44 +03:00
int err ;
2007-07-19 12:48:16 +04:00
struct vm_area_struct * vma = NULL ;
struct mm_struct * mm = bprm - > mm ;
2018-07-22 01:24:03 +03:00
bprm - > vma = vma = vm_area_alloc ( mm ) ;
2007-07-19 12:48:16 +04:00
if ( ! vma )
2009-01-07 01:40:44 +03:00
return - ENOMEM ;
mm: fix vma_is_anonymous() false-positives
vma_is_anonymous() relies on ->vm_ops being NULL to detect anonymous
VMA. This is unreliable as ->mmap may not set ->vm_ops.
False-positive vma_is_anonymous() may lead to crashes:
next ffff8801ce5e7040 prev ffff8801d20eca50 mm ffff88019c1e13c0
prot 27 anon_vma ffff88019680cdd8 vm_ops 0000000000000000
pgoff 0 file ffff8801b2ec2d00 private_data 0000000000000000
flags: 0xff(read|write|exec|shared|mayread|maywrite|mayexec|mayshare)
------------[ cut here ]------------
kernel BUG at mm/memory.c:1422!
invalid opcode: 0000 [#1] SMP KASAN
CPU: 0 PID: 18486 Comm: syz-executor3 Not tainted 4.18.0-rc3+ #136
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google
01/01/2011
RIP: 0010:zap_pmd_range mm/memory.c:1421 [inline]
RIP: 0010:zap_pud_range mm/memory.c:1466 [inline]
RIP: 0010:zap_p4d_range mm/memory.c:1487 [inline]
RIP: 0010:unmap_page_range+0x1c18/0x2220 mm/memory.c:1508
Call Trace:
unmap_single_vma+0x1a0/0x310 mm/memory.c:1553
zap_page_range_single+0x3cc/0x580 mm/memory.c:1644
unmap_mapping_range_vma mm/memory.c:2792 [inline]
unmap_mapping_range_tree mm/memory.c:2813 [inline]
unmap_mapping_pages+0x3a7/0x5b0 mm/memory.c:2845
unmap_mapping_range+0x48/0x60 mm/memory.c:2880
truncate_pagecache+0x54/0x90 mm/truncate.c:800
truncate_setsize+0x70/0xb0 mm/truncate.c:826
simple_setattr+0xe9/0x110 fs/libfs.c:409
notify_change+0xf13/0x10f0 fs/attr.c:335
do_truncate+0x1ac/0x2b0 fs/open.c:63
do_sys_ftruncate+0x492/0x560 fs/open.c:205
__do_sys_ftruncate fs/open.c:215 [inline]
__se_sys_ftruncate fs/open.c:213 [inline]
__x64_sys_ftruncate+0x59/0x80 fs/open.c:213
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
Reproducer:
#include <stdio.h>
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <unistd.h>
#include <fcntl.h>
#define KCOV_INIT_TRACE _IOR('c', 1, unsigned long)
#define KCOV_ENABLE _IO('c', 100)
#define KCOV_DISABLE _IO('c', 101)
#define COVER_SIZE (1024<<10)
#define KCOV_TRACE_PC 0
#define KCOV_TRACE_CMP 1
int main(int argc, char **argv)
{
int fd;
unsigned long *cover;
system("mount -t debugfs none /sys/kernel/debug");
fd = open("/sys/kernel/debug/kcov", O_RDWR);
ioctl(fd, KCOV_INIT_TRACE, COVER_SIZE);
cover = mmap(NULL, COVER_SIZE * sizeof(unsigned long),
PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
munmap(cover, COVER_SIZE * sizeof(unsigned long));
cover = mmap(NULL, COVER_SIZE * sizeof(unsigned long),
PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
memset(cover, 0, COVER_SIZE * sizeof(unsigned long));
ftruncate(fd, 3UL << 20);
return 0;
}
This can be fixed by assigning anonymous VMAs own vm_ops and not relying
on it being NULL.
If ->mmap() failed to set ->vm_ops, mmap_region() will set it to
dummy_vm_ops. This way we will have non-NULL ->vm_ops for all VMAs.
Link: http://lkml.kernel.org/r/20180724121139.62570-4-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: syzbot+3f84280d52be9b7083cc@syzkaller.appspotmail.com
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-07-27 02:37:35 +03:00
vma_set_anonymous ( vma ) ;
2007-07-19 12:48:16 +04:00
2016-05-24 02:26:02 +03:00
if ( down_write_killable ( & mm - > mmap_sem ) ) {
err = - EINTR ;
goto err_free ;
}
2007-07-19 12:48:16 +04:00
/*
* Place the stack at the largest stack address the architecture
* supports . Later , we ' ll move this to an appropriate place . We don ' t
* use STACK_TOP because that can depend on attributes which aren ' t
* configured yet .
*/
2011-07-27 03:08:40 +04:00
BUILD_BUG_ON ( VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP ) ;
2007-07-19 12:48:16 +04:00
vma - > vm_end = STACK_TOP_MAX ;
vma - > vm_start = vma - > vm_end - PAGE_SIZE ;
2013-09-12 01:22:24 +04:00
vma - > vm_flags = VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP ;
2007-10-19 10:39:15 +04:00
vma - > vm_page_prot = vm_get_page_prot ( vma - > vm_flags ) ;
2010-12-09 17:29:42 +03:00
2007-07-19 12:48:16 +04:00
err = insert_vm_struct ( mm , vma ) ;
2009-01-07 01:40:44 +03:00
if ( err )
2007-07-19 12:48:16 +04:00
goto err ;
mm - > stack_vm = mm - > total_vm = 1 ;
x86, mpx: On-demand kernel allocation of bounds tables
This is really the meat of the MPX patch set. If there is one patch to
review in the entire series, this is the one. There is a new ABI here
and this kernel code also interacts with userspace memory in a
relatively unusual manner. (small FAQ below).
Long Description:
This patch adds two prctl() commands to provide enable or disable the
management of bounds tables in kernel, including on-demand kernel
allocation (See the patch "on-demand kernel allocation of bounds tables")
and cleanup (See the patch "cleanup unused bound tables"). Applications
do not strictly need the kernel to manage bounds tables and we expect
some applications to use MPX without taking advantage of this kernel
support. This means the kernel can not simply infer whether an application
needs bounds table management from the MPX registers. The prctl() is an
explicit signal from userspace.
PR_MPX_ENABLE_MANAGEMENT is meant to be a signal from userspace to
require kernel's help in managing bounds tables.
PR_MPX_DISABLE_MANAGEMENT is the opposite, meaning that userspace don't
want kernel's help any more. With PR_MPX_DISABLE_MANAGEMENT, the kernel
won't allocate and free bounds tables even if the CPU supports MPX.
PR_MPX_ENABLE_MANAGEMENT will fetch the base address of the bounds
directory out of a userspace register (bndcfgu) and then cache it into
a new field (->bd_addr) in the 'mm_struct'. PR_MPX_DISABLE_MANAGEMENT
will set "bd_addr" to an invalid address. Using this scheme, we can
use "bd_addr" to determine whether the management of bounds tables in
kernel is enabled.
Also, the only way to access that bndcfgu register is via an xsaves,
which can be expensive. Caching "bd_addr" like this also helps reduce
the cost of those xsaves when doing table cleanup at munmap() time.
Unfortunately, we can not apply this optimization to #BR fault time
because we need an xsave to get the value of BNDSTATUS.
==== Why does the hardware even have these Bounds Tables? ====
MPX only has 4 hardware registers for storing bounds information.
If MPX-enabled code needs more than these 4 registers, it needs to
spill them somewhere. It has two special instructions for this
which allow the bounds to be moved between the bounds registers
and some new "bounds tables".
They are similar conceptually to a page fault and will be raised by
the MPX hardware during both bounds violations or when the tables
are not present. This patch handles those #BR exceptions for
not-present tables by carving the space out of the normal processes
address space (essentially calling the new mmap() interface indroduced
earlier in this patch set.) and then pointing the bounds-directory
over to it.
The tables *need* to be accessed and controlled by userspace because
the instructions for moving bounds in and out of them are extremely
frequent. They potentially happen every time a register pointing to
memory is dereferenced. Any direct kernel involvement (like a syscall)
to access the tables would obviously destroy performance.
==== Why not do this in userspace? ====
This patch is obviously doing this allocation in the kernel.
However, MPX does not strictly *require* anything in the kernel.
It can theoretically be done completely from userspace. Here are
a few ways this *could* be done. I don't think any of them are
practical in the real-world, but here they are.
Q: Can virtual space simply be reserved for the bounds tables so
that we never have to allocate them?
A: As noted earlier, these tables are *HUGE*. An X-GB virtual
area needs 4*X GB of virtual space, plus 2GB for the bounds
directory. If we were to preallocate them for the 128TB of
user virtual address space, we would need to reserve 512TB+2GB,
which is larger than the entire virtual address space today.
This means they can not be reserved ahead of time. Also, a
single process's pre-popualated bounds directory consumes 2GB
of virtual *AND* physical memory. IOW, it's completely
infeasible to prepopulate bounds directories.
Q: Can we preallocate bounds table space at the same time memory
is allocated which might contain pointers that might eventually
need bounds tables?
A: This would work if we could hook the site of each and every
memory allocation syscall. This can be done for small,
constrained applications. But, it isn't practical at a larger
scale since a given app has no way of controlling how all the
parts of the app might allocate memory (think libraries). The
kernel is really the only place to intercept these calls.
Q: Could a bounds fault be handed to userspace and the tables
allocated there in a signal handler instead of in the kernel?
A: (thanks to tglx) mmap() is not on the list of safe async
handler functions and even if mmap() would work it still
requires locking or nasty tricks to keep track of the
allocation state there.
Having ruled out all of the userspace-only approaches for managing
bounds tables that we could think of, we create them on demand in
the kernel.
Based-on-patch-by: Qiaowei Ren <qiaowei.ren@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: linux-mm@kvack.org
Cc: linux-mips@linux-mips.org
Cc: Dave Hansen <dave@sr71.net>
Link: http://lkml.kernel.org/r/20141114151829.AD4310DE@viggo.jf.intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-11-14 18:18:29 +03:00
arch_bprm_mm_init ( mm , vma ) ;
2007-07-19 12:48:16 +04:00
up_write ( & mm - > mmap_sem ) ;
bprm - > p = vma - > vm_end - sizeof ( void * ) ;
return 0 ;
err :
2009-01-07 01:40:44 +03:00
up_write ( & mm - > mmap_sem ) ;
2016-05-24 02:26:02 +03:00
err_free :
2009-01-07 01:40:44 +03:00
bprm - > vma = NULL ;
2018-07-21 23:48:51 +03:00
vm_area_free ( vma ) ;
2007-07-19 12:48:16 +04:00
return err ;
}
static bool valid_arg_len ( struct linux_binprm * bprm , long len )
{
return len < = MAX_ARG_STRLEN ;
}
# else
2011-03-06 20:02:54 +03:00
static inline void acct_arg_size ( struct linux_binprm * bprm , unsigned long pages )
2010-11-30 22:55:34 +03:00
{
}
2011-03-06 20:02:54 +03:00
static struct page * get_arg_page ( struct linux_binprm * bprm , unsigned long pos ,
2007-07-19 12:48:16 +04:00
int write )
{
struct page * page ;
page = bprm - > page [ pos / PAGE_SIZE ] ;
if ( ! page & & write ) {
page = alloc_page ( GFP_HIGHUSER | __GFP_ZERO ) ;
if ( ! page )
return NULL ;
bprm - > page [ pos / PAGE_SIZE ] = page ;
}
return page ;
}
static void put_arg_page ( struct page * page )
{
}
static void free_arg_page ( struct linux_binprm * bprm , int i )
{
if ( bprm - > page [ i ] ) {
__free_page ( bprm - > page [ i ] ) ;
bprm - > page [ i ] = NULL ;
}
}
static void free_arg_pages ( struct linux_binprm * bprm )
{
int i ;
for ( i = 0 ; i < MAX_ARG_PAGES ; i + + )
free_arg_page ( bprm , i ) ;
}
static void flush_arg_page ( struct linux_binprm * bprm , unsigned long pos ,
struct page * page )
{
}
static int __bprm_mm_init ( struct linux_binprm * bprm )
{
bprm - > p = PAGE_SIZE * MAX_ARG_PAGES - sizeof ( void * ) ;
return 0 ;
}
static bool valid_arg_len ( struct linux_binprm * bprm , long len )
{
return len < = bprm - > p ;
}
# endif /* CONFIG_MMU */
/*
* Create a new mm_struct and populate it with a temporary stack
* vm_area_struct . We don ' t have enough context at this point to set the stack
* flags , permissions , and offset , so we use temporary values . We ' ll update
* them later in setup_arg_pages ( ) .
*/
2013-02-20 06:16:01 +04:00
static int bprm_mm_init ( struct linux_binprm * bprm )
2007-07-19 12:48:16 +04:00
{
int err ;
struct mm_struct * mm = NULL ;
bprm - > mm = mm = mm_alloc ( ) ;
err = - ENOMEM ;
if ( ! mm )
goto err ;
2018-04-11 02:35:01 +03:00
/* Save current stack limit for all calculations made during exec. */
task_lock ( current - > group_leader ) ;
bprm - > rlim_stack = current - > signal - > rlim [ RLIMIT_STACK ] ;
task_unlock ( current - > group_leader ) ;
2007-07-19 12:48:16 +04:00
err = __bprm_mm_init ( bprm ) ;
if ( err )
goto err ;
return 0 ;
err :
if ( mm ) {
bprm - > mm = NULL ;
mmdrop ( mm ) ;
}
return err ;
}
2011-03-06 20:02:37 +03:00
struct user_arg_ptr {
2011-03-06 20:02:54 +03:00
# ifdef CONFIG_COMPAT
bool is_compat ;
# endif
union {
const char __user * const __user * native ;
# ifdef CONFIG_COMPAT
2012-09-30 21:38:55 +04:00
const compat_uptr_t __user * compat ;
2011-03-06 20:02:54 +03:00
# endif
} ptr ;
2011-03-06 20:02:37 +03:00
} ;
static const char __user * get_user_arg_ptr ( struct user_arg_ptr argv , int nr )
2011-03-06 20:02:21 +03:00
{
2011-03-06 20:02:54 +03:00
const char __user * native ;
# ifdef CONFIG_COMPAT
if ( unlikely ( argv . is_compat ) ) {
compat_uptr_t compat ;
if ( get_user ( compat , argv . ptr . compat + nr ) )
return ERR_PTR ( - EFAULT ) ;
2011-03-06 20:02:21 +03:00
2011-03-06 20:02:54 +03:00
return compat_ptr ( compat ) ;
}
# endif
if ( get_user ( native , argv . ptr . native + nr ) )
2011-03-06 20:02:21 +03:00
return ERR_PTR ( - EFAULT ) ;
2011-03-06 20:02:54 +03:00
return native ;
2011-03-06 20:02:21 +03:00
}
2005-04-17 02:20:36 +04:00
/*
* count ( ) counts the number of strings in array ARGV .
*/
2011-03-06 20:02:37 +03:00
static int count ( struct user_arg_ptr argv , int max )
2005-04-17 02:20:36 +04:00
{
int i = 0 ;
2011-03-06 20:02:54 +03:00
if ( argv . ptr . native ! = NULL ) {
2005-04-17 02:20:36 +04:00
for ( ; ; ) {
2011-03-06 20:02:21 +03:00
const char __user * p = get_user_arg_ptr ( argv , i ) ;
2005-04-17 02:20:36 +04:00
if ( ! p )
break ;
2011-03-06 20:02:21 +03:00
if ( IS_ERR ( p ) )
return - EFAULT ;
2013-01-12 02:31:48 +04:00
if ( i > = max )
2005-04-17 02:20:36 +04:00
return - E2BIG ;
2013-01-12 02:31:48 +04:00
+ + i ;
2010-09-08 06:37:06 +04:00
if ( fatal_signal_pending ( current ) )
return - ERESTARTNOHAND ;
2005-04-17 02:20:36 +04:00
cond_resched ( ) ;
}
}
return i ;
}
2019-01-04 02:28:11 +03:00
static int prepare_arg_pages ( struct linux_binprm * bprm ,
struct user_arg_ptr argv , struct user_arg_ptr envp )
{
unsigned long limit , ptr_size ;
bprm - > argc = count ( argv , MAX_ARG_STRINGS ) ;
if ( bprm - > argc < 0 )
return bprm - > argc ;
bprm - > envc = count ( envp , MAX_ARG_STRINGS ) ;
if ( bprm - > envc < 0 )
return bprm - > envc ;
/*
* Limit to 1 / 4 of the max stack size or 3 / 4 of _STK_LIM
* ( whichever is smaller ) for the argv + env strings .
* This ensures that :
* - the remaining binfmt code will not run out of stack space ,
* - the program will have a reasonable amount of stack left
* to work from .
*/
limit = _STK_LIM / 4 * 3 ;
limit = min ( limit , bprm - > rlim_stack . rlim_cur / 4 ) ;
/*
* We ' ve historically supported up to 32 pages ( ARG_MAX )
* of argument strings even with small stacks
*/
limit = max_t ( unsigned long , limit , ARG_MAX ) ;
/*
* We must account for the size of all the argv and envp pointers to
* the argv and envp strings , since they will also take up space in
* the stack . They aren ' t stored until much later when we can ' t
* signal to the parent that the child has run out of stack space .
* Instead , calculate it here so it ' s possible to fail gracefully .
*/
ptr_size = ( bprm - > argc + bprm - > envc ) * sizeof ( void * ) ;
if ( limit < = ptr_size )
return - E2BIG ;
limit - = ptr_size ;
bprm - > argmin = bprm - > p - limit ;
return 0 ;
}
2005-04-17 02:20:36 +04:00
/*
2007-07-19 12:48:16 +04:00
* ' copy_strings ( ) ' copies argument / environment strings from the old
* processes ' s memory to the new process ' s stack . The call to get_user_pages ( )
* ensures the destination page is created and not swapped out .
2005-04-17 02:20:36 +04:00
*/
2011-03-06 20:02:37 +03:00
static int copy_strings ( int argc , struct user_arg_ptr argv ,
2005-05-06 03:16:09 +04:00
struct linux_binprm * bprm )
2005-04-17 02:20:36 +04:00
{
struct page * kmapped_page = NULL ;
char * kaddr = NULL ;
2007-07-19 12:48:16 +04:00
unsigned long kpos = 0 ;
2005-04-17 02:20:36 +04:00
int ret ;
while ( argc - - > 0 ) {
2010-08-18 02:52:56 +04:00
const char __user * str ;
2005-04-17 02:20:36 +04:00
int len ;
unsigned long pos ;
2011-03-06 20:02:21 +03:00
ret = - EFAULT ;
str = get_user_arg_ptr ( argv , argc ) ;
if ( IS_ERR ( str ) )
2005-04-17 02:20:36 +04:00
goto out ;
2011-03-06 20:02:21 +03:00
len = strnlen_user ( str , MAX_ARG_STRLEN ) ;
if ( ! len )
goto out ;
ret = - E2BIG ;
if ( ! valid_arg_len ( bprm , len ) )
2005-04-17 02:20:36 +04:00
goto out ;
2007-07-19 12:48:16 +04:00
/* We're going to work our way backwords. */
2005-04-17 02:20:36 +04:00
pos = bprm - > p ;
2007-07-19 12:48:16 +04:00
str + = len ;
bprm - > p - = len ;
2019-01-04 02:28:11 +03:00
# ifdef CONFIG_MMU
if ( bprm - > p < bprm - > argmin )
goto out ;
# endif
2005-04-17 02:20:36 +04:00
while ( len > 0 ) {
int offset , bytes_to_copy ;
2010-09-08 06:37:06 +04:00
if ( fatal_signal_pending ( current ) ) {
ret = - ERESTARTNOHAND ;
goto out ;
}
2010-09-08 06:36:28 +04:00
cond_resched ( ) ;
2005-04-17 02:20:36 +04:00
offset = pos % PAGE_SIZE ;
2007-07-19 12:48:16 +04:00
if ( offset = = 0 )
offset = PAGE_SIZE ;
bytes_to_copy = offset ;
if ( bytes_to_copy > len )
bytes_to_copy = len ;
offset - = bytes_to_copy ;
pos - = bytes_to_copy ;
str - = bytes_to_copy ;
len - = bytes_to_copy ;
if ( ! kmapped_page | | kpos ! = ( pos & PAGE_MASK ) ) {
struct page * page ;
page = get_arg_page ( bprm , pos , 1 ) ;
2005-04-17 02:20:36 +04:00
if ( ! page ) {
2007-07-19 12:48:16 +04:00
ret = - E2BIG ;
2005-04-17 02:20:36 +04:00
goto out ;
}
2007-07-19 12:48:16 +04:00
if ( kmapped_page ) {
flush_kernel_dcache_page ( kmapped_page ) ;
2005-04-17 02:20:36 +04:00
kunmap ( kmapped_page ) ;
2007-07-19 12:48:16 +04:00
put_arg_page ( kmapped_page ) ;
}
2005-04-17 02:20:36 +04:00
kmapped_page = page ;
kaddr = kmap ( kmapped_page ) ;
2007-07-19 12:48:16 +04:00
kpos = pos & PAGE_MASK ;
flush_arg_page ( bprm , kpos , kmapped_page ) ;
2005-04-17 02:20:36 +04:00
}
2007-07-19 12:48:16 +04:00
if ( copy_from_user ( kaddr + offset , str , bytes_to_copy ) ) {
2005-04-17 02:20:36 +04:00
ret = - EFAULT ;
goto out ;
}
}
}
ret = 0 ;
out :
2007-07-19 12:48:16 +04:00
if ( kmapped_page ) {
flush_kernel_dcache_page ( kmapped_page ) ;
2005-04-17 02:20:36 +04:00
kunmap ( kmapped_page ) ;
2007-07-19 12:48:16 +04:00
put_arg_page ( kmapped_page ) ;
}
2005-04-17 02:20:36 +04:00
return ret ;
}
/*
* Like copy_strings , but get argv and its values from kernel memory .
*/
2011-03-06 20:02:37 +03:00
int copy_strings_kernel ( int argc , const char * const * __argv ,
2010-08-18 02:52:56 +04:00
struct linux_binprm * bprm )
2005-04-17 02:20:36 +04:00
{
int r ;
mm_segment_t oldfs = get_fs ( ) ;
2011-03-06 20:02:37 +03:00
struct user_arg_ptr argv = {
2011-03-06 20:02:54 +03:00
. ptr . native = ( const char __user * const __user * ) __argv ,
2011-03-06 20:02:37 +03:00
} ;
2005-04-17 02:20:36 +04:00
set_fs ( KERNEL_DS ) ;
2011-03-06 20:02:37 +03:00
r = copy_strings ( argc , argv , bprm ) ;
2005-04-17 02:20:36 +04:00
set_fs ( oldfs ) ;
2011-03-06 20:02:37 +03:00
2005-04-17 02:20:36 +04:00
return r ;
}
EXPORT_SYMBOL ( copy_strings_kernel ) ;
# ifdef CONFIG_MMU
2007-07-19 12:48:16 +04:00
2005-04-17 02:20:36 +04:00
/*
2007-07-19 12:48:16 +04:00
* During bprm_mm_init ( ) , we create a temporary stack at STACK_TOP_MAX . Once
* the binfmt code determines where the new stack should reside , we shift it to
* its final location . The process proceeds as follows :
2005-04-17 02:20:36 +04:00
*
2007-07-19 12:48:16 +04:00
* 1 ) Use shift to calculate the new vma endpoints .
* 2 ) Extend vma to cover both the old and new ranges . This ensures the
* arguments passed to subsequent functions are consistent .
* 3 ) Move vma ' s page tables to the new range .
* 4 ) Free up any cleared pgd range .
* 5 ) Shrink the vma to cover only the new range .
2005-04-17 02:20:36 +04:00
*/
2007-07-19 12:48:16 +04:00
static int shift_arg_pages ( struct vm_area_struct * vma , unsigned long shift )
2005-04-17 02:20:36 +04:00
{
struct mm_struct * mm = vma - > vm_mm ;
2007-07-19 12:48:16 +04:00
unsigned long old_start = vma - > vm_start ;
unsigned long old_end = vma - > vm_end ;
unsigned long length = old_end - old_start ;
unsigned long new_start = old_start - shift ;
unsigned long new_end = old_end - shift ;
2011-05-25 04:11:45 +04:00
struct mmu_gather tlb ;
2005-04-17 02:20:36 +04:00
2007-07-19 12:48:16 +04:00
BUG_ON ( new_start > new_end ) ;
2005-04-17 02:20:36 +04:00
2007-07-19 12:48:16 +04:00
/*
* ensure there are no vmas between where we want to go
* and where we are
*/
if ( vma ! = find_vma ( mm , new_start ) )
return - EFAULT ;
/*
* cover the whole range : [ new_start , old_end )
*/
mm: change anon_vma linking to fix multi-process server scalability issue
The old anon_vma code can lead to scalability issues with heavily forking
workloads. Specifically, each anon_vma will be shared between the parent
process and all its child processes.
In a workload with 1000 child processes and a VMA with 1000 anonymous
pages per process that get COWed, this leads to a system with a million
anonymous pages in the same anon_vma, each of which is mapped in just one
of the 1000 processes. However, the current rmap code needs to walk them
all, leading to O(N) scanning complexity for each page.
This can result in systems where one CPU is walking the page tables of
1000 processes in page_referenced_one, while all other CPUs are stuck on
the anon_vma lock. This leads to catastrophic failure for a benchmark
like AIM7, where the total number of processes can reach in the tens of
thousands. Real workloads are still a factor 10 less process intensive
than AIM7, but they are catching up.
This patch changes the way anon_vmas and VMAs are linked, which allows us
to associate multiple anon_vmas with a VMA. At fork time, each child
process gets its own anon_vmas, in which its COWed pages will be
instantiated. The parents' anon_vma is also linked to the VMA, because
non-COWed pages could be present in any of the children.
This reduces rmap scanning complexity to O(1) for the pages of the 1000
child processes, with O(N) complexity for at most 1/N pages in the system.
This reduces the average scanning cost in heavily forking workloads from
O(N) to 2.
The only real complexity in this patch stems from the fact that linking a
VMA to anon_vmas now involves memory allocations. This means vma_adjust
can fail, if it needs to attach a VMA to anon_vma structures. This in
turn means error handling needs to be added to the calling functions.
A second source of complexity is that, because there can be multiple
anon_vmas, the anon_vma linking in vma_adjust can no longer be done under
"the" anon_vma lock. To prevent the rmap code from walking up an
incomplete VMA, this patch introduces the VM_LOCK_RMAP VMA flag. This bit
flag uses the same slot as the NOMMU VM_MAPPED_COPY, with an ifdef in mm.h
to make sure it is impossible to compile a kernel that needs both symbolic
values for the same bitflag.
Some test results:
Without the anon_vma changes, when AIM7 hits around 9.7k users (on a test
box with 16GB RAM and not quite enough IO), the system ends up running
>99% in system time, with every CPU on the same anon_vma lock in the
pageout code.
With these changes, AIM7 hits the cross-over point around 29.7k users.
This happens with ~99% IO wait time, there never seems to be any spike in
system time. The anon_vma lock contention appears to be resolved.
[akpm@linux-foundation.org: cleanups]
Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Larry Woodman <lwoodman@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-03-06 00:42:07 +03:00
if ( vma_adjust ( vma , new_start , old_end , vma - > vm_pgoff , NULL ) )
return - ENOMEM ;
2007-07-19 12:48:16 +04:00
/*
* move the page tables downwards , on failure we rely on
* process cleanup to remove whatever mess we made .
*/
if ( length ! = move_page_tables ( vma , old_start ,
2012-10-09 03:31:50 +04:00
vma , new_start , length , false ) )
2007-07-19 12:48:16 +04:00
return - ENOMEM ;
lru_add_drain ( ) ;
Fix TLB gather virtual address range invalidation corner cases
Ben Tebulin reported:
"Since v3.7.2 on two independent machines a very specific Git
repository fails in 9/10 cases on git-fsck due to an SHA1/memory
failures. This only occurs on a very specific repository and can be
reproduced stably on two independent laptops. Git mailing list ran
out of ideas and for me this looks like some very exotic kernel issue"
and bisected the failure to the backport of commit 53a59fc67f97 ("mm:
limit mmu_gather batching to fix soft lockups on !CONFIG_PREEMPT").
That commit itself is not actually buggy, but what it does is to make it
much more likely to hit the partial TLB invalidation case, since it
introduces a new case in tlb_next_batch() that previously only ever
happened when running out of memory.
The real bug is that the TLB gather virtual memory range setup is subtly
buggered. It was introduced in commit 597e1c3580b7 ("mm/mmu_gather:
enable tlb flush range in generic mmu_gather"), and the range handling
was already fixed at least once in commit e6c495a96ce0 ("mm: fix the TLB
range flushed when __tlb_remove_page() runs out of slots"), but that fix
was not complete.
The problem with the TLB gather virtual address range is that it isn't
set up by the initial tlb_gather_mmu() initialization (which didn't get
the TLB range information), but it is set up ad-hoc later by the
functions that actually flush the TLB. And so any such case that forgot
to update the TLB range entries would potentially miss TLB invalidates.
Rather than try to figure out exactly which particular ad-hoc range
setup was missing (I personally suspect it's the hugetlb case in
zap_huge_pmd(), which didn't have the same logic as zap_pte_range()
did), this patch just gets rid of the problem at the source: make the
TLB range information available to tlb_gather_mmu(), and initialize it
when initializing all the other tlb gather fields.
This makes the patch larger, but conceptually much simpler. And the end
result is much more understandable; even if you want to play games with
partial ranges when invalidating the TLB contents in chunks, now the
range information is always there, and anybody who doesn't want to
bother with it won't introduce subtle bugs.
Ben verified that this fixes his problem.
Reported-bisected-and-tested-by: Ben Tebulin <tebulin@googlemail.com>
Build-testing-by: Stephen Rothwell <sfr@canb.auug.org.au>
Build-testing-by: Richard Weinberger <richard.weinberger@gmail.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-08-15 22:42:25 +04:00
tlb_gather_mmu ( & tlb , mm , old_start , old_end ) ;
2007-07-19 12:48:16 +04:00
if ( new_end > old_start ) {
/*
* when the old and new regions overlap clear from new_end .
*/
2011-05-25 04:11:45 +04:00
free_pgd_range ( & tlb , new_end , old_end , new_end ,
2013-04-30 02:07:44 +04:00
vma - > vm_next ? vma - > vm_next - > vm_start : USER_PGTABLES_CEILING ) ;
2007-07-19 12:48:16 +04:00
} else {
/*
* otherwise , clean from old_start ; this is done to not touch
* the address space in [ new_end , old_start ) some architectures
* have constraints on va - space that make this illegal ( IA64 ) -
* for the others its just a little faster .
*/
2011-05-25 04:11:45 +04:00
free_pgd_range ( & tlb , old_start , old_end , new_end ,
2013-04-30 02:07:44 +04:00
vma - > vm_next ? vma - > vm_next - > vm_start : USER_PGTABLES_CEILING ) ;
2005-04-17 02:20:36 +04:00
}
Fix TLB gather virtual address range invalidation corner cases
Ben Tebulin reported:
"Since v3.7.2 on two independent machines a very specific Git
repository fails in 9/10 cases on git-fsck due to an SHA1/memory
failures. This only occurs on a very specific repository and can be
reproduced stably on two independent laptops. Git mailing list ran
out of ideas and for me this looks like some very exotic kernel issue"
and bisected the failure to the backport of commit 53a59fc67f97 ("mm:
limit mmu_gather batching to fix soft lockups on !CONFIG_PREEMPT").
That commit itself is not actually buggy, but what it does is to make it
much more likely to hit the partial TLB invalidation case, since it
introduces a new case in tlb_next_batch() that previously only ever
happened when running out of memory.
The real bug is that the TLB gather virtual memory range setup is subtly
buggered. It was introduced in commit 597e1c3580b7 ("mm/mmu_gather:
enable tlb flush range in generic mmu_gather"), and the range handling
was already fixed at least once in commit e6c495a96ce0 ("mm: fix the TLB
range flushed when __tlb_remove_page() runs out of slots"), but that fix
was not complete.
The problem with the TLB gather virtual address range is that it isn't
set up by the initial tlb_gather_mmu() initialization (which didn't get
the TLB range information), but it is set up ad-hoc later by the
functions that actually flush the TLB. And so any such case that forgot
to update the TLB range entries would potentially miss TLB invalidates.
Rather than try to figure out exactly which particular ad-hoc range
setup was missing (I personally suspect it's the hugetlb case in
zap_huge_pmd(), which didn't have the same logic as zap_pte_range()
did), this patch just gets rid of the problem at the source: make the
TLB range information available to tlb_gather_mmu(), and initialize it
when initializing all the other tlb gather fields.
This makes the patch larger, but conceptually much simpler. And the end
result is much more understandable; even if you want to play games with
partial ranges when invalidating the TLB contents in chunks, now the
range information is always there, and anybody who doesn't want to
bother with it won't introduce subtle bugs.
Ben verified that this fixes his problem.
Reported-bisected-and-tested-by: Ben Tebulin <tebulin@googlemail.com>
Build-testing-by: Stephen Rothwell <sfr@canb.auug.org.au>
Build-testing-by: Richard Weinberger <richard.weinberger@gmail.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-08-15 22:42:25 +04:00
tlb_finish_mmu ( & tlb , old_start , old_end ) ;
2007-07-19 12:48:16 +04:00
/*
mm: change anon_vma linking to fix multi-process server scalability issue
The old anon_vma code can lead to scalability issues with heavily forking
workloads. Specifically, each anon_vma will be shared between the parent
process and all its child processes.
In a workload with 1000 child processes and a VMA with 1000 anonymous
pages per process that get COWed, this leads to a system with a million
anonymous pages in the same anon_vma, each of which is mapped in just one
of the 1000 processes. However, the current rmap code needs to walk them
all, leading to O(N) scanning complexity for each page.
This can result in systems where one CPU is walking the page tables of
1000 processes in page_referenced_one, while all other CPUs are stuck on
the anon_vma lock. This leads to catastrophic failure for a benchmark
like AIM7, where the total number of processes can reach in the tens of
thousands. Real workloads are still a factor 10 less process intensive
than AIM7, but they are catching up.
This patch changes the way anon_vmas and VMAs are linked, which allows us
to associate multiple anon_vmas with a VMA. At fork time, each child
process gets its own anon_vmas, in which its COWed pages will be
instantiated. The parents' anon_vma is also linked to the VMA, because
non-COWed pages could be present in any of the children.
This reduces rmap scanning complexity to O(1) for the pages of the 1000
child processes, with O(N) complexity for at most 1/N pages in the system.
This reduces the average scanning cost in heavily forking workloads from
O(N) to 2.
The only real complexity in this patch stems from the fact that linking a
VMA to anon_vmas now involves memory allocations. This means vma_adjust
can fail, if it needs to attach a VMA to anon_vma structures. This in
turn means error handling needs to be added to the calling functions.
A second source of complexity is that, because there can be multiple
anon_vmas, the anon_vma linking in vma_adjust can no longer be done under
"the" anon_vma lock. To prevent the rmap code from walking up an
incomplete VMA, this patch introduces the VM_LOCK_RMAP VMA flag. This bit
flag uses the same slot as the NOMMU VM_MAPPED_COPY, with an ifdef in mm.h
to make sure it is impossible to compile a kernel that needs both symbolic
values for the same bitflag.
Some test results:
Without the anon_vma changes, when AIM7 hits around 9.7k users (on a test
box with 16GB RAM and not quite enough IO), the system ends up running
>99% in system time, with every CPU on the same anon_vma lock in the
pageout code.
With these changes, AIM7 hits the cross-over point around 29.7k users.
This happens with ~99% IO wait time, there never seems to be any spike in
system time. The anon_vma lock contention appears to be resolved.
[akpm@linux-foundation.org: cleanups]
Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Larry Woodman <lwoodman@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-03-06 00:42:07 +03:00
* Shrink the vma to just the new range . Always succeeds .
2007-07-19 12:48:16 +04:00
*/
vma_adjust ( vma , new_start , new_end , vma - > vm_pgoff , NULL ) ;
return 0 ;
2005-04-17 02:20:36 +04:00
}
2007-07-19 12:48:16 +04:00
/*
* Finalizes the stack vm_area_struct . The flags and permissions are updated ,
* the stack is optionally relocated , and some extra space is added .
*/
2005-04-17 02:20:36 +04:00
int setup_arg_pages ( struct linux_binprm * bprm ,
unsigned long stack_top ,
int executable_stack )
{
2007-07-19 12:48:16 +04:00
unsigned long ret ;
unsigned long stack_shift ;
2005-04-17 02:20:36 +04:00
struct mm_struct * mm = current - > mm ;
2007-07-19 12:48:16 +04:00
struct vm_area_struct * vma = bprm - > vma ;
struct vm_area_struct * prev = NULL ;
unsigned long vm_flags ;
unsigned long stack_base ;
2010-02-11 00:56:42 +03:00
unsigned long stack_size ;
unsigned long stack_expand ;
unsigned long rlim_stack ;
2005-04-17 02:20:36 +04:00
# ifdef CONFIG_STACK_GROWSUP
2014-05-14 02:58:24 +04:00
/* Limit stack size */
2018-04-11 02:35:01 +03:00
stack_base = bprm - > rlim_stack . rlim_max ;
2014-05-14 02:58:24 +04:00
if ( stack_base > STACK_SIZE_MAX )
stack_base = STACK_SIZE_MAX ;
2005-04-17 02:20:36 +04:00
2015-05-11 23:01:27 +03:00
/* Add space for stack randomization. */
stack_base + = ( STACK_RND_MASK < < PAGE_SHIFT ) ;
2007-07-19 12:48:16 +04:00
/* Make sure we didn't let the argument array grow too large. */
if ( vma - > vm_end - vma - > vm_start > stack_base )
return - ENOMEM ;
2005-04-17 02:20:36 +04:00
2007-07-19 12:48:16 +04:00
stack_base = PAGE_ALIGN ( stack_top - stack_base ) ;
2005-04-17 02:20:36 +04:00
2007-07-19 12:48:16 +04:00
stack_shift = vma - > vm_start - stack_base ;
mm - > arg_start = bprm - > p - stack_shift ;
bprm - > p = vma - > vm_end - stack_shift ;
2005-04-17 02:20:36 +04:00
# else
2007-07-19 12:48:16 +04:00
stack_top = arch_align_stack ( stack_top ) ;
stack_top = PAGE_ALIGN ( stack_top ) ;
2010-09-08 06:35:49 +04:00
if ( unlikely ( stack_top < mmap_min_addr ) | |
unlikely ( vma - > vm_end - vma - > vm_start > = stack_top - mmap_min_addr ) )
return - ENOMEM ;
2007-07-19 12:48:16 +04:00
stack_shift = vma - > vm_end - stack_top ;
bprm - > p - = stack_shift ;
2005-04-17 02:20:36 +04:00
mm - > arg_start = bprm - > p ;
# endif
if ( bprm - > loader )
2007-07-19 12:48:16 +04:00
bprm - > loader - = stack_shift ;
bprm - > exec - = stack_shift ;
2005-04-17 02:20:36 +04:00
2016-05-24 02:26:02 +03:00
if ( down_write_killable ( & mm - > mmap_sem ) )
return - EINTR ;
2008-07-11 00:19:20 +04:00
vm_flags = VM_STACK_FLAGS ;
2007-07-19 12:48:16 +04:00
/*
* Adjust stack execute permissions ; explicitly enable for
* EXSTACK_ENABLE_X , disable for EXSTACK_DISABLE_X and leave alone
* ( arch default ) otherwise .
*/
if ( unlikely ( executable_stack = = EXSTACK_ENABLE_X ) )
vm_flags | = VM_EXEC ;
else if ( executable_stack = = EXSTACK_DISABLE_X )
vm_flags & = ~ VM_EXEC ;
vm_flags | = mm - > def_flags ;
2010-05-25 01:32:24 +04:00
vm_flags | = VM_STACK_INCOMPLETE_SETUP ;
2007-07-19 12:48:16 +04:00
ret = mprotect_fixup ( vma , & prev , vma - > vm_start , vma - > vm_end ,
vm_flags ) ;
if ( ret )
goto out_unlock ;
BUG_ON ( prev ! = vma ) ;
/* Move stack pages down in memory. */
if ( stack_shift ) {
ret = shift_arg_pages ( vma , stack_shift ) ;
2009-11-12 01:26:48 +03:00
if ( ret )
goto out_unlock ;
2005-04-17 02:20:36 +04:00
}
2010-05-25 01:32:24 +04:00
/* mprotect_fixup is overkill to remove the temporary stack flags */
vma - > vm_flags & = ~ VM_STACK_INCOMPLETE_SETUP ;
2010-03-06 00:42:57 +03:00
stack_expand = 131072UL ; /* randomly 32*4k (or 2*64k) pages */
2010-02-11 00:56:42 +03:00
stack_size = vma - > vm_end - vma - > vm_start ;
/*
* Align this down to a page boundary as expand_stack
* will align it up .
*/
2018-04-11 02:35:01 +03:00
rlim_stack = bprm - > rlim_stack . rlim_cur & PAGE_MASK ;
2007-07-19 12:48:16 +04:00
# ifdef CONFIG_STACK_GROWSUP
2010-02-11 00:56:42 +03:00
if ( stack_size + stack_expand > rlim_stack )
stack_base = vma - > vm_start + rlim_stack ;
else
stack_base = vma - > vm_end + stack_expand ;
2007-07-19 12:48:16 +04:00
# else
2010-02-11 00:56:42 +03:00
if ( stack_size + stack_expand > rlim_stack )
stack_base = vma - > vm_end - rlim_stack ;
else
stack_base = vma - > vm_start - stack_expand ;
2007-07-19 12:48:16 +04:00
# endif
2010-05-18 18:30:49 +04:00
current - > mm - > start_stack = bprm - > p ;
2007-07-19 12:48:16 +04:00
ret = expand_stack ( vma , stack_base ) ;
if ( ret )
ret = - EFAULT ;
out_unlock :
2005-04-17 02:20:36 +04:00
up_write ( & mm - > mmap_sem ) ;
2009-11-12 01:26:48 +03:00
return ret ;
2005-04-17 02:20:36 +04:00
}
EXPORT_SYMBOL ( setup_arg_pages ) ;
2016-07-24 18:30:18 +03:00
# else
/*
* Transfer the program arguments and environment from the holding pages
* onto the stack . The provided stack pointer is adjusted accordingly .
*/
int transfer_args_to_stack ( struct linux_binprm * bprm ,
unsigned long * sp_location )
{
unsigned long index , stop , sp ;
int ret = 0 ;
stop = bprm - > p > > PAGE_SHIFT ;
sp = * sp_location ;
for ( index = MAX_ARG_PAGES - 1 ; index > = stop ; index - - ) {
unsigned int offset = index = = stop ? bprm - > p & ~ PAGE_MASK : 0 ;
char * src = kmap ( bprm - > page [ index ] ) + offset ;
sp - = PAGE_SIZE - offset ;
if ( copy_to_user ( ( void * ) sp , src , PAGE_SIZE - offset ) ! = 0 )
ret = - EFAULT ;
kunmap ( bprm - > page [ index ] ) ;
if ( ret )
goto out ;
}
* sp_location = sp ;
out :
return ret ;
}
EXPORT_SYMBOL ( transfer_args_to_stack ) ;
2005-04-17 02:20:36 +04:00
# endif /* CONFIG_MMU */
syscalls: implement execveat() system call
This patchset adds execveat(2) for x86, and is derived from Meredydd
Luff's patch from Sept 2012 (https://lkml.org/lkml/2012/9/11/528).
The primary aim of adding an execveat syscall is to allow an
implementation of fexecve(3) that does not rely on the /proc filesystem,
at least for executables (rather than scripts). The current glibc version
of fexecve(3) is implemented via /proc, which causes problems in sandboxed
or otherwise restricted environments.
Given the desire for a /proc-free fexecve() implementation, HPA suggested
(https://lkml.org/lkml/2006/7/11/556) that an execveat(2) syscall would be
an appropriate generalization.
Also, having a new syscall means that it can take a flags argument without
back-compatibility concerns. The current implementation just defines the
AT_EMPTY_PATH and AT_SYMLINK_NOFOLLOW flags, but other flags could be
added in future -- for example, flags for new namespaces (as suggested at
https://lkml.org/lkml/2006/7/11/474).
Related history:
- https://lkml.org/lkml/2006/12/27/123 is an example of someone
realizing that fexecve() is likely to fail in a chroot environment.
- http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043 covered
documenting the /proc requirement of fexecve(3) in its manpage, to
"prevent other people from wasting their time".
- https://bugzilla.redhat.com/show_bug.cgi?id=241609 described a
problem where a process that did setuid() could not fexecve()
because it no longer had access to /proc/self/fd; this has since
been fixed.
This patch (of 4):
Add a new execveat(2) system call. execveat() is to execve() as openat()
is to open(): it takes a file descriptor that refers to a directory, and
resolves the filename relative to that.
In addition, if the filename is empty and AT_EMPTY_PATH is specified,
execveat() executes the file to which the file descriptor refers. This
replicates the functionality of fexecve(), which is a system call in other
UNIXen, but in Linux glibc it depends on opening "/proc/self/fd/<fd>" (and
so relies on /proc being mounted).
The filename fed to the executed program as argv[0] (or the name of the
script fed to a script interpreter) will be of the form "/dev/fd/<fd>"
(for an empty filename) or "/dev/fd/<fd>/<filename>", effectively
reflecting how the executable was found. This does however mean that
execution of a script in a /proc-less environment won't work; also, script
execution via an O_CLOEXEC file descriptor fails (as the file will not be
accessible after exec).
Based on patches by Meredydd Luff.
Signed-off-by: David Drysdale <drysdale@google.com>
Cc: Meredydd Luff <meredydd@senatehouse.org>
Cc: Shuah Khan <shuah.kh@samsung.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rich Felker <dalias@aerifal.cx>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-13 03:57:29 +03:00
static struct file * do_open_execat ( int fd , struct filename * name , int flags )
2005-04-17 02:20:36 +04:00
{
struct file * file ;
2008-05-19 09:53:34 +04:00
int err ;
syscalls: implement execveat() system call
This patchset adds execveat(2) for x86, and is derived from Meredydd
Luff's patch from Sept 2012 (https://lkml.org/lkml/2012/9/11/528).
The primary aim of adding an execveat syscall is to allow an
implementation of fexecve(3) that does not rely on the /proc filesystem,
at least for executables (rather than scripts). The current glibc version
of fexecve(3) is implemented via /proc, which causes problems in sandboxed
or otherwise restricted environments.
Given the desire for a /proc-free fexecve() implementation, HPA suggested
(https://lkml.org/lkml/2006/7/11/556) that an execveat(2) syscall would be
an appropriate generalization.
Also, having a new syscall means that it can take a flags argument without
back-compatibility concerns. The current implementation just defines the
AT_EMPTY_PATH and AT_SYMLINK_NOFOLLOW flags, but other flags could be
added in future -- for example, flags for new namespaces (as suggested at
https://lkml.org/lkml/2006/7/11/474).
Related history:
- https://lkml.org/lkml/2006/12/27/123 is an example of someone
realizing that fexecve() is likely to fail in a chroot environment.
- http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043 covered
documenting the /proc requirement of fexecve(3) in its manpage, to
"prevent other people from wasting their time".
- https://bugzilla.redhat.com/show_bug.cgi?id=241609 described a
problem where a process that did setuid() could not fexecve()
because it no longer had access to /proc/self/fd; this has since
been fixed.
This patch (of 4):
Add a new execveat(2) system call. execveat() is to execve() as openat()
is to open(): it takes a file descriptor that refers to a directory, and
resolves the filename relative to that.
In addition, if the filename is empty and AT_EMPTY_PATH is specified,
execveat() executes the file to which the file descriptor refers. This
replicates the functionality of fexecve(), which is a system call in other
UNIXen, but in Linux glibc it depends on opening "/proc/self/fd/<fd>" (and
so relies on /proc being mounted).
The filename fed to the executed program as argv[0] (or the name of the
script fed to a script interpreter) will be of the form "/dev/fd/<fd>"
(for an empty filename) or "/dev/fd/<fd>/<filename>", effectively
reflecting how the executable was found. This does however mean that
execution of a script in a /proc-less environment won't work; also, script
execution via an O_CLOEXEC file descriptor fails (as the file will not be
accessible after exec).
Based on patches by Meredydd Luff.
Signed-off-by: David Drysdale <drysdale@google.com>
Cc: Meredydd Luff <meredydd@senatehouse.org>
Cc: Shuah Khan <shuah.kh@samsung.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rich Felker <dalias@aerifal.cx>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-13 03:57:29 +03:00
struct open_flags open_exec_flags = {
2011-02-24 01:44:09 +03:00
. open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC ,
2015-12-27 06:33:24 +03:00
. acc_mode = MAY_EXEC ,
2013-06-11 08:23:01 +04:00
. intent = LOOKUP_OPEN ,
. lookup_flags = LOOKUP_FOLLOW ,
2011-02-24 01:44:09 +03:00
} ;
2005-04-17 02:20:36 +04:00
syscalls: implement execveat() system call
This patchset adds execveat(2) for x86, and is derived from Meredydd
Luff's patch from Sept 2012 (https://lkml.org/lkml/2012/9/11/528).
The primary aim of adding an execveat syscall is to allow an
implementation of fexecve(3) that does not rely on the /proc filesystem,
at least for executables (rather than scripts). The current glibc version
of fexecve(3) is implemented via /proc, which causes problems in sandboxed
or otherwise restricted environments.
Given the desire for a /proc-free fexecve() implementation, HPA suggested
(https://lkml.org/lkml/2006/7/11/556) that an execveat(2) syscall would be
an appropriate generalization.
Also, having a new syscall means that it can take a flags argument without
back-compatibility concerns. The current implementation just defines the
AT_EMPTY_PATH and AT_SYMLINK_NOFOLLOW flags, but other flags could be
added in future -- for example, flags for new namespaces (as suggested at
https://lkml.org/lkml/2006/7/11/474).
Related history:
- https://lkml.org/lkml/2006/12/27/123 is an example of someone
realizing that fexecve() is likely to fail in a chroot environment.
- http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043 covered
documenting the /proc requirement of fexecve(3) in its manpage, to
"prevent other people from wasting their time".
- https://bugzilla.redhat.com/show_bug.cgi?id=241609 described a
problem where a process that did setuid() could not fexecve()
because it no longer had access to /proc/self/fd; this has since
been fixed.
This patch (of 4):
Add a new execveat(2) system call. execveat() is to execve() as openat()
is to open(): it takes a file descriptor that refers to a directory, and
resolves the filename relative to that.
In addition, if the filename is empty and AT_EMPTY_PATH is specified,
execveat() executes the file to which the file descriptor refers. This
replicates the functionality of fexecve(), which is a system call in other
UNIXen, but in Linux glibc it depends on opening "/proc/self/fd/<fd>" (and
so relies on /proc being mounted).
The filename fed to the executed program as argv[0] (or the name of the
script fed to a script interpreter) will be of the form "/dev/fd/<fd>"
(for an empty filename) or "/dev/fd/<fd>/<filename>", effectively
reflecting how the executable was found. This does however mean that
execution of a script in a /proc-less environment won't work; also, script
execution via an O_CLOEXEC file descriptor fails (as the file will not be
accessible after exec).
Based on patches by Meredydd Luff.
Signed-off-by: David Drysdale <drysdale@google.com>
Cc: Meredydd Luff <meredydd@senatehouse.org>
Cc: Shuah Khan <shuah.kh@samsung.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rich Felker <dalias@aerifal.cx>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-13 03:57:29 +03:00
if ( ( flags & ~ ( AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH ) ) ! = 0 )
return ERR_PTR ( - EINVAL ) ;
if ( flags & AT_SYMLINK_NOFOLLOW )
open_exec_flags . lookup_flags & = ~ LOOKUP_FOLLOW ;
if ( flags & AT_EMPTY_PATH )
open_exec_flags . lookup_flags | = LOOKUP_EMPTY ;
file = do_filp_open ( fd , name , & open_exec_flags ) ;
2009-04-06 19:16:22 +04:00
if ( IS_ERR ( file ) )
2008-05-19 09:53:34 +04:00
goto out ;
err = - EACCES ;
2013-01-24 02:07:38 +04:00
if ( ! S_ISREG ( file_inode ( file ) - > i_mode ) )
2009-04-06 19:16:22 +04:00
goto exit ;
2008-05-19 09:53:34 +04:00
2015-06-29 22:42:03 +03:00
if ( path_noexec ( & file - > f_path ) )
2009-04-06 19:16:22 +04:00
goto exit ;
2008-05-19 09:53:34 +04:00
err = deny_write_access ( file ) ;
2009-04-06 19:16:22 +04:00
if ( err )
goto exit ;
2005-04-17 02:20:36 +04:00
syscalls: implement execveat() system call
This patchset adds execveat(2) for x86, and is derived from Meredydd
Luff's patch from Sept 2012 (https://lkml.org/lkml/2012/9/11/528).
The primary aim of adding an execveat syscall is to allow an
implementation of fexecve(3) that does not rely on the /proc filesystem,
at least for executables (rather than scripts). The current glibc version
of fexecve(3) is implemented via /proc, which causes problems in sandboxed
or otherwise restricted environments.
Given the desire for a /proc-free fexecve() implementation, HPA suggested
(https://lkml.org/lkml/2006/7/11/556) that an execveat(2) syscall would be
an appropriate generalization.
Also, having a new syscall means that it can take a flags argument without
back-compatibility concerns. The current implementation just defines the
AT_EMPTY_PATH and AT_SYMLINK_NOFOLLOW flags, but other flags could be
added in future -- for example, flags for new namespaces (as suggested at
https://lkml.org/lkml/2006/7/11/474).
Related history:
- https://lkml.org/lkml/2006/12/27/123 is an example of someone
realizing that fexecve() is likely to fail in a chroot environment.
- http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043 covered
documenting the /proc requirement of fexecve(3) in its manpage, to
"prevent other people from wasting their time".
- https://bugzilla.redhat.com/show_bug.cgi?id=241609 described a
problem where a process that did setuid() could not fexecve()
because it no longer had access to /proc/self/fd; this has since
been fixed.
This patch (of 4):
Add a new execveat(2) system call. execveat() is to execve() as openat()
is to open(): it takes a file descriptor that refers to a directory, and
resolves the filename relative to that.
In addition, if the filename is empty and AT_EMPTY_PATH is specified,
execveat() executes the file to which the file descriptor refers. This
replicates the functionality of fexecve(), which is a system call in other
UNIXen, but in Linux glibc it depends on opening "/proc/self/fd/<fd>" (and
so relies on /proc being mounted).
The filename fed to the executed program as argv[0] (or the name of the
script fed to a script interpreter) will be of the form "/dev/fd/<fd>"
(for an empty filename) or "/dev/fd/<fd>/<filename>", effectively
reflecting how the executable was found. This does however mean that
execution of a script in a /proc-less environment won't work; also, script
execution via an O_CLOEXEC file descriptor fails (as the file will not be
accessible after exec).
Based on patches by Meredydd Luff.
Signed-off-by: David Drysdale <drysdale@google.com>
Cc: Meredydd Luff <meredydd@senatehouse.org>
Cc: Shuah Khan <shuah.kh@samsung.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rich Felker <dalias@aerifal.cx>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-13 03:57:29 +03:00
if ( name - > name [ 0 ] ! = ' \0 ' )
fsnotify_open ( file ) ;
2009-04-06 19:16:22 +04:00
out :
2008-05-19 09:53:34 +04:00
return file ;
2009-04-06 19:16:22 +04:00
exit :
fput ( file ) ;
2008-05-19 09:53:34 +04:00
return ERR_PTR ( err ) ;
}
2014-02-06 00:54:53 +04:00
struct file * open_exec ( const char * name )
{
2015-01-22 08:00:03 +03:00
struct filename * filename = getname_kernel ( name ) ;
struct file * f = ERR_CAST ( filename ) ;
if ( ! IS_ERR ( filename ) ) {
f = do_open_execat ( AT_FDCWD , filename , 0 ) ;
putname ( filename ) ;
}
return f ;
2014-02-06 00:54:53 +04:00
}
2005-04-17 02:20:36 +04:00
EXPORT_SYMBOL ( open_exec ) ;
2015-12-29 00:02:29 +03:00
int kernel_read_file ( struct file * file , void * * buf , loff_t * size ,
2016-01-24 18:07:32 +03:00
loff_t max_size , enum kernel_read_file_id id )
2015-12-29 00:02:29 +03:00
{
loff_t i_size , pos ;
ssize_t bytes = 0 ;
int ret ;
if ( ! S_ISREG ( file_inode ( file ) - > i_mode ) | | max_size < 0 )
return - EINVAL ;
2018-03-09 22:30:20 +03:00
ret = deny_write_access ( file ) ;
2016-01-31 06:23:26 +03:00
if ( ret )
return ret ;
2018-03-09 22:30:20 +03:00
ret = security_kernel_read_file ( file , id ) ;
2014-10-26 13:42:07 +03:00
if ( ret )
2018-03-09 22:30:20 +03:00
goto out ;
2014-10-26 13:42:07 +03:00
2015-12-29 00:02:29 +03:00
i_size = i_size_read ( file_inode ( file ) ) ;
2014-10-26 13:42:07 +03:00
if ( i_size < = 0 ) {
ret = - EINVAL ;
goto out ;
}
2018-09-07 22:16:24 +03:00
if ( i_size > SIZE_MAX | | ( max_size > 0 & & i_size > max_size ) ) {
ret = - EFBIG ;
goto out ;
}
2015-12-29 00:02:29 +03:00
2016-08-03 00:04:28 +03:00
if ( id ! = READING_FIRMWARE_PREALLOC_BUFFER )
* buf = vmalloc ( i_size ) ;
2014-10-26 13:42:07 +03:00
if ( ! * buf ) {
ret = - ENOMEM ;
goto out ;
}
2015-12-29 00:02:29 +03:00
pos = 0 ;
while ( pos < i_size ) {
2017-09-01 18:39:13 +03:00
bytes = kernel_read ( file , * buf + pos , i_size - pos , & pos ) ;
2015-12-29 00:02:29 +03:00
if ( bytes < 0 ) {
ret = bytes ;
2019-02-19 05:10:38 +03:00
goto out_free ;
2015-12-29 00:02:29 +03:00
}
if ( bytes = = 0 )
break ;
}
if ( pos ! = i_size ) {
ret = - EIO ;
2014-10-26 13:42:07 +03:00
goto out_free ;
2015-12-29 00:02:29 +03:00
}
2016-01-24 18:07:32 +03:00
ret = security_kernel_post_read_file ( file , * buf , i_size , id ) ;
2015-12-29 00:02:29 +03:00
if ( ! ret )
* size = pos ;
2014-10-26 13:42:07 +03:00
out_free :
2015-12-29 00:02:29 +03:00
if ( ret < 0 ) {
2016-08-03 00:04:28 +03:00
if ( id ! = READING_FIRMWARE_PREALLOC_BUFFER ) {
vfree ( * buf ) ;
* buf = NULL ;
}
2015-12-29 00:02:29 +03:00
}
2014-10-26 13:42:07 +03:00
out :
allow_write_access ( file ) ;
2015-12-29 00:02:29 +03:00
return ret ;
}
EXPORT_SYMBOL_GPL ( kernel_read_file ) ;
2017-09-13 05:45:33 +03:00
int kernel_read_file_from_path ( const char * path , void * * buf , loff_t * size ,
2015-11-19 20:39:22 +03:00
loff_t max_size , enum kernel_read_file_id id )
{
struct file * file ;
int ret ;
if ( ! path | | ! * path )
return - EINVAL ;
file = filp_open ( path , O_RDONLY , 0 ) ;
if ( IS_ERR ( file ) )
return PTR_ERR ( file ) ;
ret = kernel_read_file ( file , buf , size , max_size , id ) ;
fput ( file ) ;
return ret ;
}
EXPORT_SYMBOL_GPL ( kernel_read_file_from_path ) ;
2016-02-01 16:36:21 +03:00
int kernel_read_file_from_fd ( int fd , void * * buf , loff_t * size , loff_t max_size ,
enum kernel_read_file_id id )
{
struct fd f = fdget ( fd ) ;
int ret = - EBADF ;
if ( ! f . file )
goto out ;
ret = kernel_read_file ( f . file , buf , size , max_size , id ) ;
out :
fdput ( f ) ;
return ret ;
}
EXPORT_SYMBOL_GPL ( kernel_read_file_from_fd ) ;
2013-04-14 04:31:37 +04:00
ssize_t read_code ( struct file * file , unsigned long addr , loff_t pos , size_t len )
{
2014-02-05 04:08:21 +04:00
ssize_t res = vfs_read ( file , ( void __user * ) addr , len , & pos ) ;
2013-04-14 04:31:37 +04:00
if ( res > 0 )
flush_icache_range ( addr , addr + len ) ;
return res ;
}
EXPORT_SYMBOL ( read_code ) ;
2005-04-17 02:20:36 +04:00
static int exec_mmap ( struct mm_struct * mm )
{
struct task_struct * tsk ;
mm: per-thread vma caching
This patch is a continuation of efforts trying to optimize find_vma(),
avoiding potentially expensive rbtree walks to locate a vma upon faults.
The original approach (https://lkml.org/lkml/2013/11/1/410), where the
largest vma was also cached, ended up being too specific and random,
thus further comparison with other approaches were needed. There are
two things to consider when dealing with this, the cache hit rate and
the latency of find_vma(). Improving the hit-rate does not necessarily
translate in finding the vma any faster, as the overhead of any fancy
caching schemes can be too high to consider.
We currently cache the last used vma for the whole address space, which
provides a nice optimization, reducing the total cycles in find_vma() by
up to 250%, for workloads with good locality. On the other hand, this
simple scheme is pretty much useless for workloads with poor locality.
Analyzing ebizzy runs shows that, no matter how many threads are
running, the mmap_cache hit rate is less than 2%, and in many situations
below 1%.
The proposed approach is to replace this scheme with a small per-thread
cache, maximizing hit rates at a very low maintenance cost.
Invalidations are performed by simply bumping up a 32-bit sequence
number. The only expensive operation is in the rare case of a seq
number overflow, where all caches that share the same address space are
flushed. Upon a miss, the proposed replacement policy is based on the
page number that contains the virtual address in question. Concretely,
the following results are seen on an 80 core, 8 socket x86-64 box:
1) System bootup: Most programs are single threaded, so the per-thread
scheme does improve ~50% hit rate by just adding a few more slots to
the cache.
+----------------+----------+------------------+
| caching scheme | hit-rate | cycles (billion) |
+----------------+----------+------------------+
| baseline | 50.61% | 19.90 |
| patched | 73.45% | 13.58 |
+----------------+----------+------------------+
2) Kernel build: This one is already pretty good with the current
approach as we're dealing with good locality.
+----------------+----------+------------------+
| caching scheme | hit-rate | cycles (billion) |
+----------------+----------+------------------+
| baseline | 75.28% | 11.03 |
| patched | 88.09% | 9.31 |
+----------------+----------+------------------+
3) Oracle 11g Data Mining (4k pages): Similar to the kernel build workload.
+----------------+----------+------------------+
| caching scheme | hit-rate | cycles (billion) |
+----------------+----------+------------------+
| baseline | 70.66% | 17.14 |
| patched | 91.15% | 12.57 |
+----------------+----------+------------------+
4) Ebizzy: There's a fair amount of variation from run to run, but this
approach always shows nearly perfect hit rates, while baseline is just
about non-existent. The amounts of cycles can fluctuate between
anywhere from ~60 to ~116 for the baseline scheme, but this approach
reduces it considerably. For instance, with 80 threads:
+----------------+----------+------------------+
| caching scheme | hit-rate | cycles (billion) |
+----------------+----------+------------------+
| baseline | 1.06% | 91.54 |
| patched | 99.97% | 14.18 |
+----------------+----------+------------------+
[akpm@linux-foundation.org: fix nommu build, per Davidlohr]
[akpm@linux-foundation.org: document vmacache_valid() logic]
[akpm@linux-foundation.org: attempt to untangle header files]
[akpm@linux-foundation.org: add vmacache_find() BUG_ON]
[hughd@google.com: add vmacache_valid_mm() (from Oleg)]
[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: adjust and enhance comments]
Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Michel Lespinasse <walken@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Tested-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-04-08 02:37:25 +04:00
struct mm_struct * old_mm , * active_mm ;
2005-04-17 02:20:36 +04:00
/* Notify parent that we're no longer interested in the old VM */
tsk = current ;
old_mm = current - > mm ;
2019-11-07 00:55:38 +03:00
exec_mm_release ( tsk , old_mm ) ;
2005-04-17 02:20:36 +04:00
if ( old_mm ) {
2012-06-20 23:53:01 +04:00
sync_mm_rss ( old_mm ) ;
2005-04-17 02:20:36 +04:00
/*
* Make sure that if there is a core dump in progress
* for the old mm , we get out and die instead of going
* through with the exec . We must hold mmap_sem around
2008-07-25 12:47:41 +04:00
* checking core_state and changing tsk - > mm .
2005-04-17 02:20:36 +04:00
*/
down_read ( & old_mm - > mmap_sem ) ;
2008-07-25 12:47:41 +04:00
if ( unlikely ( old_mm - > core_state ) ) {
2005-04-17 02:20:36 +04:00
up_read ( & old_mm - > mmap_sem ) ;
return - EINTR ;
}
}
task_lock ( tsk ) ;
active_mm = tsk - > active_mm ;
2019-09-19 20:37:02 +03:00
membarrier_exec_mmap ( mm ) ;
2005-04-17 02:20:36 +04:00
tsk - > mm = mm ;
tsk - > active_mm = mm ;
activate_mm ( active_mm , mm ) ;
mm: per-thread vma caching
This patch is a continuation of efforts trying to optimize find_vma(),
avoiding potentially expensive rbtree walks to locate a vma upon faults.
The original approach (https://lkml.org/lkml/2013/11/1/410), where the
largest vma was also cached, ended up being too specific and random,
thus further comparison with other approaches were needed. There are
two things to consider when dealing with this, the cache hit rate and
the latency of find_vma(). Improving the hit-rate does not necessarily
translate in finding the vma any faster, as the overhead of any fancy
caching schemes can be too high to consider.
We currently cache the last used vma for the whole address space, which
provides a nice optimization, reducing the total cycles in find_vma() by
up to 250%, for workloads with good locality. On the other hand, this
simple scheme is pretty much useless for workloads with poor locality.
Analyzing ebizzy runs shows that, no matter how many threads are
running, the mmap_cache hit rate is less than 2%, and in many situations
below 1%.
The proposed approach is to replace this scheme with a small per-thread
cache, maximizing hit rates at a very low maintenance cost.
Invalidations are performed by simply bumping up a 32-bit sequence
number. The only expensive operation is in the rare case of a seq
number overflow, where all caches that share the same address space are
flushed. Upon a miss, the proposed replacement policy is based on the
page number that contains the virtual address in question. Concretely,
the following results are seen on an 80 core, 8 socket x86-64 box:
1) System bootup: Most programs are single threaded, so the per-thread
scheme does improve ~50% hit rate by just adding a few more slots to
the cache.
+----------------+----------+------------------+
| caching scheme | hit-rate | cycles (billion) |
+----------------+----------+------------------+
| baseline | 50.61% | 19.90 |
| patched | 73.45% | 13.58 |
+----------------+----------+------------------+
2) Kernel build: This one is already pretty good with the current
approach as we're dealing with good locality.
+----------------+----------+------------------+
| caching scheme | hit-rate | cycles (billion) |
+----------------+----------+------------------+
| baseline | 75.28% | 11.03 |
| patched | 88.09% | 9.31 |
+----------------+----------+------------------+
3) Oracle 11g Data Mining (4k pages): Similar to the kernel build workload.
+----------------+----------+------------------+
| caching scheme | hit-rate | cycles (billion) |
+----------------+----------+------------------+
| baseline | 70.66% | 17.14 |
| patched | 91.15% | 12.57 |
+----------------+----------+------------------+
4) Ebizzy: There's a fair amount of variation from run to run, but this
approach always shows nearly perfect hit rates, while baseline is just
about non-existent. The amounts of cycles can fluctuate between
anywhere from ~60 to ~116 for the baseline scheme, but this approach
reduces it considerably. For instance, with 80 threads:
+----------------+----------+------------------+
| caching scheme | hit-rate | cycles (billion) |
+----------------+----------+------------------+
| baseline | 1.06% | 91.54 |
| patched | 99.97% | 14.18 |
+----------------+----------+------------------+
[akpm@linux-foundation.org: fix nommu build, per Davidlohr]
[akpm@linux-foundation.org: document vmacache_valid() logic]
[akpm@linux-foundation.org: attempt to untangle header files]
[akpm@linux-foundation.org: add vmacache_find() BUG_ON]
[hughd@google.com: add vmacache_valid_mm() (from Oleg)]
[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: adjust and enhance comments]
Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Michel Lespinasse <walken@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Tested-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-04-08 02:37:25 +04:00
tsk - > mm - > vmacache_seqnum = 0 ;
vmacache_flush ( tsk ) ;
2005-04-17 02:20:36 +04:00
task_unlock ( tsk ) ;
if ( old_mm ) {
up_read ( & old_mm - > mmap_sem ) ;
2006-04-01 03:13:38 +04:00
BUG_ON ( active_mm ! = old_mm ) ;
2012-03-19 20:04:01 +04:00
setmax_mm_hiwater_rss ( & tsk - > signal - > maxrss , old_mm ) ;
mm owner: fix race between swapoff and exit
There's a race between mm->owner assignment and swapoff, more easily
seen when task slab poisoning is turned on. The condition occurs when
try_to_unuse() runs in parallel with an exiting task. A similar race
can occur with callers of get_task_mm(), such as /proc/<pid>/<mmstats>
or ptrace or page migration.
CPU0 CPU1
try_to_unuse
looks at mm = task0->mm
increments mm->mm_users
task 0 exits
mm->owner needs to be updated, but no
new owner is found (mm_users > 1, but
no other task has task->mm = task0->mm)
mm_update_next_owner() leaves
mmput(mm) decrements mm->mm_users
task0 freed
dereferencing mm->owner fails
The fix is to notify the subsystem via mm_owner_changed callback(),
if no new owner is found, by specifying the new task as NULL.
Jiri Slaby:
mm->owner was set to NULL prior to calling cgroup_mm_owner_callbacks(), but
must be set after that, so as not to pass NULL as old owner causing oops.
Daisuke Nishimura:
mm_update_next_owner() may set mm->owner to NULL, but mem_cgroup_from_task()
and its callers need to take account of this situation to avoid oops.
Hugh Dickins:
Lockdep warning and hang below exec_mmap() when testing these patches.
exit_mm() up_reads mmap_sem before calling mm_update_next_owner(),
so exec_mmap() now needs to do the same. And with that repositioning,
there's now no point in mm_need_new_owner() allowing for NULL mm.
Reported-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-09-29 02:09:31 +04:00
mm_update_next_owner ( old_mm ) ;
2005-04-17 02:20:36 +04:00
mmput ( old_mm ) ;
return 0 ;
}
mmdrop ( active_mm ) ;
return 0 ;
}
/*
* This function makes sure the current process has its own signal table ,
* so that flush_signal_handlers can later reset the handlers without
* disturbing other processes . ( Other processes might share the signal
* table via the CLONE_SIGHAND option to clone ( ) . )
*/
2006-01-15 00:20:43 +03:00
static int de_thread ( struct task_struct * tsk )
2005-04-17 02:20:36 +04:00
{
struct signal_struct * sig = tsk - > signal ;
2007-10-17 10:27:22 +04:00
struct sighand_struct * oldsighand = tsk - > sighand ;
2005-04-17 02:20:36 +04:00
spinlock_t * lock = & oldsighand - > siglock ;
2006-09-27 12:51:13 +04:00
if ( thread_group_empty ( tsk ) )
2005-04-17 02:20:36 +04:00
goto no_thread_group ;
/*
* Kill all other threads in the thread group .
*/
spin_lock_irq ( lock ) ;
2008-02-05 09:27:24 +03:00
if ( signal_group_exit ( sig ) ) {
2005-04-17 02:20:36 +04:00
/*
* Another group action in progress , just
* return so that the signal is processed .
*/
spin_unlock_irq ( lock ) ;
return - EAGAIN ;
}
2010-05-27 01:43:11 +04:00
2008-02-05 09:27:24 +03:00
sig - > group_exit_task = tsk ;
2010-05-27 01:43:11 +04:00
sig - > notify_count = zap_other_threads ( tsk ) ;
if ( ! thread_group_leader ( tsk ) )
sig - > notify_count - - ;
2005-04-17 02:20:36 +04:00
2010-05-27 01:43:11 +04:00
while ( sig - > notify_count ) {
2012-10-08 21:13:01 +04:00
__set_current_state ( TASK_KILLABLE ) ;
2005-04-17 02:20:36 +04:00
spin_unlock_irq ( lock ) ;
2018-12-03 15:04:18 +03:00
schedule ( ) ;
2019-01-04 02:28:58 +03:00
if ( __fatal_signal_pending ( tsk ) )
2012-10-08 21:13:01 +04:00
goto killed ;
2005-04-17 02:20:36 +04:00
spin_lock_irq ( lock ) ;
}
spin_unlock_irq ( lock ) ;
/*
* At this point all other threads have exited , all we have to
* do is to wait for the thread group leader to become inactive ,
* and to assume its PID :
*/
2006-09-27 12:51:13 +04:00
if ( ! thread_group_leader ( tsk ) ) {
2008-12-02 01:18:16 +03:00
struct task_struct * leader = tsk - > group_leader ;
2007-10-17 10:27:23 +04:00
for ( ; ; ) {
2017-02-02 13:50:56 +03:00
cgroup_threadgroup_change_begin ( tsk ) ;
2007-10-17 10:27:23 +04:00
write_lock_irq ( & tasklist_lock ) ;
2015-04-16 22:48:01 +03:00
/*
* Do this under tasklist_lock to ensure that
* exit_notify ( ) can ' t miss - > group_exit_task
*/
sig - > notify_count = - 1 ;
2007-10-17 10:27:23 +04:00
if ( likely ( leader - > exit_state ) )
break ;
2012-10-08 21:13:01 +04:00
__set_current_state ( TASK_KILLABLE ) ;
2007-10-17 10:27:23 +04:00
write_unlock_irq ( & tasklist_lock ) ;
2017-02-02 13:50:56 +03:00
cgroup_threadgroup_change_end ( tsk ) ;
2018-12-03 15:04:18 +03:00
schedule ( ) ;
2019-01-04 02:28:58 +03:00
if ( __fatal_signal_pending ( tsk ) )
2012-10-08 21:13:01 +04:00
goto killed ;
2007-10-17 10:27:23 +04:00
}
2005-04-17 02:20:36 +04:00
2006-04-11 09:54:16 +04:00
/*
* The only record we have of the real - time age of a
* process , regardless of execs it ' s done , is start_time .
* All the past CPU time is accumulated in signal_struct
* from sister threads now dead . But in this non - leader
* exec , nothing survives from the original leader thread ,
* whose birth marks the true age of this process now .
* When we take on its identity by switching to its PID , we
* also take its birthdate ( always earlier than our own ) .
*/
2006-09-27 12:51:13 +04:00
tsk - > start_time = leader - > start_time ;
2013-07-04 02:08:35 +04:00
tsk - > real_start_time = leader - > real_start_time ;
2006-04-11 09:54:16 +04:00
2007-10-19 10:40:18 +04:00
BUG_ON ( ! same_thread_group ( leader , tsk ) ) ;
BUG_ON ( has_group_leader_pid ( tsk ) ) ;
2005-04-17 02:20:36 +04:00
/*
* An exec ( ) starts a new thread group with the
* TGID of the previous thread group . Rehash the
* two threads with a switched PID , and release
* the former thread group leader :
*/
2006-03-29 04:11:03 +04:00
/* Become a process group leader with the old leader's pid.
2006-09-27 12:51:06 +04:00
* The old leader becomes a thread of the this thread group .
* Note : The old leader also uses this pid until release_task
2006-03-29 04:11:03 +04:00
* is called . Odd but simple and correct .
*/
2006-09-27 12:51:13 +04:00
tsk - > pid = leader - > pid ;
2013-07-04 02:08:25 +04:00
change_pid ( tsk , PIDTYPE_PID , task_pid ( leader ) ) ;
2017-06-04 12:32:13 +03:00
transfer_pid ( leader , tsk , PIDTYPE_TGID ) ;
2006-09-27 12:51:13 +04:00
transfer_pid ( leader , tsk , PIDTYPE_PGID ) ;
transfer_pid ( leader , tsk , PIDTYPE_SID ) ;
2009-12-18 02:27:15 +03:00
2006-09-27 12:51:13 +04:00
list_replace_rcu ( & leader - > tasks , & tsk - > tasks ) ;
2009-12-18 02:27:15 +03:00
list_replace_init ( & leader - > sibling , & tsk - > sibling ) ;
2005-04-17 02:20:36 +04:00
2006-09-27 12:51:13 +04:00
tsk - > group_leader = tsk ;
leader - > group_leader = tsk ;
2006-04-11 03:16:49 +04:00
2006-09-27 12:51:13 +04:00
tsk - > exit_signal = SIGCHLD ;
2011-06-23 01:10:26 +04:00
leader - > exit_signal = - 1 ;
2005-11-24 00:37:43 +03:00
BUG_ON ( leader - > exit_state ! = EXIT_ZOMBIE ) ;
leader - > exit_state = EXIT_DEAD ;
ptrace: do_wait(traced_leader_killed_by_mt_exec) can block forever
Test-case:
void *tfunc(void *arg)
{
execvp("true", NULL);
return NULL;
}
int main(void)
{
int pid;
if (fork()) {
pthread_t t;
kill(getpid(), SIGSTOP);
pthread_create(&t, NULL, tfunc, NULL);
for (;;)
pause();
}
pid = getppid();
assert(ptrace(PTRACE_ATTACH, pid, 0,0) == 0);
while (wait(NULL) > 0)
ptrace(PTRACE_CONT, pid, 0,0);
return 0;
}
It is racy, exit_notify() does __wake_up_parent() too. But in the
likely case it triggers the problem: de_thread() does release_task()
and the old leader goes away without the notification, the tracer
sleeps in do_wait() without children/tracees.
Change de_thread() to do __wake_up_parent(traced_leader->parent).
Since it is already EXIT_DEAD we can do this without ptrace_unlink(),
EXIT_DEAD threads do not exist from do_wait's pov.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
2011-07-21 22:00:43 +04:00
/*
* We are going to release_task ( ) - > ptrace_unlink ( ) silently ,
* the tracer can sleep in do_wait ( ) . EXIT_DEAD guarantees
* the tracer wont ' t block again waiting for this thread .
*/
if ( unlikely ( leader - > ptrace ) )
__wake_up_parent ( leader , leader - > parent ) ;
2005-04-17 02:20:36 +04:00
write_unlock_irq ( & tasklist_lock ) ;
2017-02-02 13:50:56 +03:00
cgroup_threadgroup_change_end ( tsk ) ;
2008-12-02 01:18:16 +03:00
release_task ( leader ) ;
2008-02-05 09:27:24 +03:00
}
2005-04-17 02:20:36 +04:00
2007-10-17 10:27:23 +04:00
sig - > group_exit_task = NULL ;
sig - > notify_count = 0 ;
2005-04-17 02:20:36 +04:00
no_thread_group :
2012-03-19 20:03:22 +04:00
/* we have changed execution domain */
tsk - > exit_signal = SIGCHLD ;
posix-timers: Make them configurable
Some embedded systems have no use for them. This removes about
25KB from the kernel binary size when configured out.
Corresponding syscalls are routed to a stub logging the attempt to
use those syscalls which should be enough of a clue if they were
disabled without proper consideration. They are: timer_create,
timer_gettime: timer_getoverrun, timer_settime, timer_delete,
clock_adjtime, setitimer, getitimer, alarm.
The clock_settime, clock_gettime, clock_getres and clock_nanosleep
syscalls are replaced by simple wrappers compatible with CLOCK_REALTIME,
CLOCK_MONOTONIC and CLOCK_BOOTTIME only which should cover the vast
majority of use cases with very little code.
Signed-off-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <john.stultz@linaro.org>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Cc: Paul Bolle <pebolle@tiscali.nl>
Cc: linux-kbuild@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: Michal Marek <mmarek@suse.com>
Cc: Edward Cree <ecree@solarflare.com>
Link: http://lkml.kernel.org/r/1478841010-28605-7-git-send-email-nicolas.pitre@linaro.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-11-11 08:10:10 +03:00
# ifdef CONFIG_POSIX_TIMERS
2005-04-17 02:20:36 +04:00
exit_itimers ( sig ) ;
2008-05-26 20:55:42 +04:00
flush_itimer_signals ( ) ;
posix-timers: Make them configurable
Some embedded systems have no use for them. This removes about
25KB from the kernel binary size when configured out.
Corresponding syscalls are routed to a stub logging the attempt to
use those syscalls which should be enough of a clue if they were
disabled without proper consideration. They are: timer_create,
timer_gettime: timer_getoverrun, timer_settime, timer_delete,
clock_adjtime, setitimer, getitimer, alarm.
The clock_settime, clock_gettime, clock_getres and clock_nanosleep
syscalls are replaced by simple wrappers compatible with CLOCK_REALTIME,
CLOCK_MONOTONIC and CLOCK_BOOTTIME only which should cover the vast
majority of use cases with very little code.
Signed-off-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <john.stultz@linaro.org>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Cc: Paul Bolle <pebolle@tiscali.nl>
Cc: linux-kbuild@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: Michal Marek <mmarek@suse.com>
Cc: Edward Cree <ecree@solarflare.com>
Link: http://lkml.kernel.org/r/1478841010-28605-7-git-send-email-nicolas.pitre@linaro.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-11-11 08:10:10 +03:00
# endif
2005-11-07 21:12:43 +03:00
2019-01-18 15:27:26 +03:00
if ( refcount_read ( & oldsighand - > count ) ! = 1 ) {
2007-10-17 10:27:22 +04:00
struct sighand_struct * newsighand ;
2005-04-17 02:20:36 +04:00
/*
2007-10-17 10:27:22 +04:00
* This - > sighand is shared with the CLONE_SIGHAND
* but not CLONE_THREAD task , switch to the new one .
2005-04-17 02:20:36 +04:00
*/
2007-10-17 10:27:22 +04:00
newsighand = kmem_cache_alloc ( sighand_cachep , GFP_KERNEL ) ;
if ( ! newsighand )
return - ENOMEM ;
2019-01-18 15:27:26 +03:00
refcount_set ( & newsighand - > count , 1 ) ;
2005-04-17 02:20:36 +04:00
memcpy ( newsighand - > action , oldsighand - > action ,
sizeof ( newsighand - > action ) ) ;
write_lock_irq ( & tasklist_lock ) ;
spin_lock ( & oldsighand - > siglock ) ;
2006-09-27 12:51:13 +04:00
rcu_assign_pointer ( tsk - > sighand , newsighand ) ;
2005-04-17 02:20:36 +04:00
spin_unlock ( & oldsighand - > siglock ) ;
write_unlock_irq ( & tasklist_lock ) ;
signal/timer/event: signalfd core
This patch series implements the new signalfd() system call.
I took part of the original Linus code (and you know how badly it can be
broken :), and I added even more breakage ;) Signals are fetched from the same
signal queue used by the process, so signalfd will compete with standard
kernel delivery in dequeue_signal(). If you want to reliably fetch signals on
the signalfd file, you need to block them with sigprocmask(SIG_BLOCK). This
seems to be working fine on my Dual Opteron machine. I made a quick test
program for it:
http://www.xmailserver.org/signafd-test.c
The signalfd() system call implements signal delivery into a file descriptor
receiver. The signalfd file descriptor if created with the following API:
int signalfd(int ufd, const sigset_t *mask, size_t masksize);
The "ufd" parameter allows to change an existing signalfd sigmask, w/out going
to close/create cycle (Linus idea). Use "ufd" == -1 if you want a brand new
signalfd file.
The "mask" allows to specify the signal mask of signals that we are interested
in. The "masksize" parameter is the size of "mask".
The signalfd fd supports the poll(2) and read(2) system calls. The poll(2)
will return POLLIN when signals are available to be dequeued. As a direct
consequence of supporting the Linux poll subsystem, the signalfd fd can use
used together with epoll(2) too.
The read(2) system call will return a "struct signalfd_siginfo" structure in
the userspace supplied buffer. The return value is the number of bytes copied
in the supplied buffer, or -1 in case of error. The read(2) call can also
return 0, in case the sighand structure to which the signalfd was attached,
has been orphaned. The O_NONBLOCK flag is also supported, and read(2) will
return -EAGAIN in case no signal is available.
If the size of the buffer passed to read(2) is lower than sizeof(struct
signalfd_siginfo), -EINVAL is returned. A read from the signalfd can also
return -ERESTARTSYS in case a signal hits the process. The format of the
struct signalfd_siginfo is, and the valid fields depends of the (->code &
__SI_MASK) value, in the same way a struct siginfo would:
struct signalfd_siginfo {
__u32 signo; /* si_signo */
__s32 err; /* si_errno */
__s32 code; /* si_code */
__u32 pid; /* si_pid */
__u32 uid; /* si_uid */
__s32 fd; /* si_fd */
__u32 tid; /* si_fd */
__u32 band; /* si_band */
__u32 overrun; /* si_overrun */
__u32 trapno; /* si_trapno */
__s32 status; /* si_status */
__s32 svint; /* si_int */
__u64 svptr; /* si_ptr */
__u64 utime; /* si_utime */
__u64 stime; /* si_stime */
__u64 addr; /* si_addr */
};
[akpm@linux-foundation.org: fix signalfd_copyinfo() on i386]
Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-11 09:23:13 +04:00
__cleanup_sighand ( oldsighand ) ;
2005-04-17 02:20:36 +04:00
}
2006-09-27 12:51:13 +04:00
BUG_ON ( ! thread_group_leader ( tsk ) ) ;
2005-04-17 02:20:36 +04:00
return 0 ;
2012-10-08 21:13:01 +04:00
killed :
/* protects against exit_notify() and __exit_signal() */
read_lock ( & tasklist_lock ) ;
sig - > group_exit_task = NULL ;
sig - > notify_count = 0 ;
read_unlock ( & tasklist_lock ) ;
return - EAGAIN ;
2005-04-17 02:20:36 +04:00
}
2007-10-17 10:27:22 +04:00
2017-12-15 02:32:41 +03:00
char * __get_task_comm ( char * buf , size_t buf_size , struct task_struct * tsk )
2005-04-17 02:20:36 +04:00
{
task_lock ( tsk ) ;
2017-12-15 02:32:41 +03:00
strncpy ( buf , tsk - > comm , buf_size ) ;
2005-04-17 02:20:36 +04:00
task_unlock ( tsk ) ;
2008-02-05 09:27:21 +03:00
return buf ;
2005-04-17 02:20:36 +04:00
}
2017-12-15 02:32:41 +03:00
EXPORT_SYMBOL_GPL ( __get_task_comm ) ;
2005-04-17 02:20:36 +04:00
2012-08-21 17:56:33 +04:00
/*
* These functions flushes out all traces of the currently running executable
* so that a new one can be started
*/
2014-05-28 12:45:04 +04:00
void __set_task_comm ( struct task_struct * tsk , const char * buf , bool exec )
2005-04-17 02:20:36 +04:00
{
task_lock ( tsk ) ;
2012-01-11 03:08:09 +04:00
trace_task_rename ( tsk , buf ) ;
2005-04-17 02:20:36 +04:00
strlcpy ( tsk - > comm , buf , sizeof ( tsk - > comm ) ) ;
task_unlock ( tsk ) ;
2014-05-28 12:45:04 +04:00
perf_event_comm ( tsk , exec ) ;
2005-04-17 02:20:36 +04:00
}
exec: Correct comments about "point of no return"
In commit 221af7f87b97 ("Split 'flush_old_exec' into two functions"),
the comment about the point of no return should have stayed in
flush_old_exec() since it refers to "bprm->mm = NULL;" line, but prior
changes in commits c89681ed7d0e ("remove steal_locks()"), and
fd8328be874f ("sanitize handling of shared descriptor tables in failing
execve()") made it look like it meant the current->sas_ss_sp line instead.
The comment was referring to the fact that once bprm->mm is NULL, all
failures from a binfmt load_binary hook (e.g. load_elf_binary), will
get SEGV raised against current. Move this comment and expand the
explanation a bit, putting it above the assignment this time, and add
details about the true nature of "point of no return" being the call
to flush_old_exec() itself.
This also removes an erroneous commet about when credentials are being
installed. That has its own dedicated function, install_exec_creds(),
which carries a similar (and correct) comment, so remove the bogus comment
where installation is not actually happening.
Cc: David Howells <dhowells@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Serge Hallyn <serge@hallyn.com>
2017-07-19 01:25:30 +03:00
/*
* Calling this is the point of no return . None of the failures will be
* seen by userspace since either the process is already taking a fatal
* signal ( via de_thread ( ) or coredump ) , or will have SEGV raised
* ( after exec_mmap ( ) ) by search_binary_handlers ( see below ) .
*/
2005-04-17 02:20:36 +04:00
int flush_old_exec ( struct linux_binprm * bprm )
{
Split 'flush_old_exec' into two functions
'flush_old_exec()' is the point of no return when doing an execve(), and
it is pretty badly misnamed. It doesn't just flush the old executable
environment, it also starts up the new one.
Which is very inconvenient for things like setting up the new
personality, because we want the new personality to affect the starting
of the new environment, but at the same time we do _not_ want the new
personality to take effect if flushing the old one fails.
As a result, the x86-64 '32-bit' personality is actually done using this
insane "I'm going to change the ABI, but I haven't done it yet" bit
(TIF_ABI_PENDING), with SET_PERSONALITY() not actually setting the
personality, but just the "pending" bit, so that "flush_thread()" can do
the actual personality magic.
This patch in no way changes any of that insanity, but it does split the
'flush_old_exec()' function up into a preparatory part that can fail
(still called flush_old_exec()), and a new part that will actually set
up the new exec environment (setup_new_exec()). All callers are changed
to trivially comply with the new world order.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-01-29 09:14:42 +03:00
int retval ;
2005-04-17 02:20:36 +04:00
/*
* Make sure we have a private signal table and that
* we are unassociated from the previous thread group .
*/
retval = de_thread ( current ) ;
if ( retval )
goto out ;
2015-04-16 22:47:59 +03:00
/*
* Must be called _before_ exec_mmap ( ) as bprm - > mm is
* not visibile until then . This also enables the update
* to be lockless .
*/
2008-04-29 12:01:36 +04:00
set_mm_exe_file ( bprm - > mm , bprm - > file ) ;
2015-04-16 22:47:59 +03:00
2005-04-17 02:20:36 +04:00
/*
* Release all of the old mmap stuff
*/
2010-11-30 22:55:34 +03:00
acct_arg_size ( bprm , 0 ) ;
2005-04-17 02:20:36 +04:00
retval = exec_mmap ( bprm - > mm ) ;
if ( retval )
2008-04-22 13:11:59 +04:00
goto out ;
2005-04-17 02:20:36 +04:00
exec: Correct comments about "point of no return"
In commit 221af7f87b97 ("Split 'flush_old_exec' into two functions"),
the comment about the point of no return should have stayed in
flush_old_exec() since it refers to "bprm->mm = NULL;" line, but prior
changes in commits c89681ed7d0e ("remove steal_locks()"), and
fd8328be874f ("sanitize handling of shared descriptor tables in failing
execve()") made it look like it meant the current->sas_ss_sp line instead.
The comment was referring to the fact that once bprm->mm is NULL, all
failures from a binfmt load_binary hook (e.g. load_elf_binary), will
get SEGV raised against current. Move this comment and expand the
explanation a bit, putting it above the assignment this time, and add
details about the true nature of "point of no return" being the call
to flush_old_exec() itself.
This also removes an erroneous commet about when credentials are being
installed. That has its own dedicated function, install_exec_creds(),
which carries a similar (and correct) comment, so remove the bogus comment
where installation is not actually happening.
Cc: David Howells <dhowells@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Serge Hallyn <serge@hallyn.com>
2017-07-19 01:25:30 +03:00
/*
* After clearing bprm - > mm ( to mark that current is using the
* prepared mm now ) , we have nothing left of the original
* process . If anything from here on returns an error , the check
* in search_binary_handler ( ) will SEGV current .
*/
bprm - > mm = NULL ;
2010-02-02 23:37:44 +03:00
2011-06-09 22:05:18 +04:00
set_fs ( USER_DS ) ;
2014-01-24 03:55:57 +04:00
current - > flags & = ~ ( PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
PF_NOFREEZE | PF_NO_SETAFFINITY ) ;
2010-02-02 23:37:44 +03:00
flush_thread ( ) ;
current - > personality & = ~ bprm - > per_clear ;
2016-12-21 08:26:24 +03:00
/*
* We have to apply CLOEXEC before we change whether the process is
* dumpable ( in setup_new_exec ) to avoid a race with a process in userspace
* trying to access the should - be - closed file descriptors of a process
* undergoing exec ( 2 ) .
*/
do_close_on_exec ( current - > files ) ;
Split 'flush_old_exec' into two functions
'flush_old_exec()' is the point of no return when doing an execve(), and
it is pretty badly misnamed. It doesn't just flush the old executable
environment, it also starts up the new one.
Which is very inconvenient for things like setting up the new
personality, because we want the new personality to affect the starting
of the new environment, but at the same time we do _not_ want the new
personality to take effect if flushing the old one fails.
As a result, the x86-64 '32-bit' personality is actually done using this
insane "I'm going to change the ABI, but I haven't done it yet" bit
(TIF_ABI_PENDING), with SET_PERSONALITY() not actually setting the
personality, but just the "pending" bit, so that "flush_thread()" can do
the actual personality magic.
This patch in no way changes any of that insanity, but it does split the
'flush_old_exec()' function up into a preparatory part that can fail
(still called flush_old_exec()), and a new part that will actually set
up the new exec environment (setup_new_exec()). All callers are changed
to trivially comply with the new world order.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-01-29 09:14:42 +03:00
return 0 ;
out :
return retval ;
}
EXPORT_SYMBOL ( flush_old_exec ) ;
2011-06-19 20:49:47 +04:00
void would_dump ( struct linux_binprm * bprm , struct file * file )
{
2016-11-17 07:06:51 +03:00
struct inode * inode = file_inode ( file ) ;
if ( inode_permission ( inode , MAY_READ ) < 0 ) {
struct user_namespace * old , * user_ns ;
2011-06-19 20:49:47 +04:00
bprm - > interp_flags | = BINPRM_FLAGS_ENFORCE_NONDUMP ;
2016-11-17 07:06:51 +03:00
/* Ensure mm->user_ns contains the executable */
user_ns = old = bprm - > mm - > user_ns ;
while ( ( user_ns ! = & init_user_ns ) & &
! privileged_wrt_inode_uidgid ( user_ns , inode ) )
user_ns = user_ns - > parent ;
if ( old ! = user_ns ) {
bprm - > mm - > user_ns = get_user_ns ( user_ns ) ;
put_user_ns ( old ) ;
}
}
2011-06-19 20:49:47 +04:00
}
EXPORT_SYMBOL ( would_dump ) ;
Split 'flush_old_exec' into two functions
'flush_old_exec()' is the point of no return when doing an execve(), and
it is pretty badly misnamed. It doesn't just flush the old executable
environment, it also starts up the new one.
Which is very inconvenient for things like setting up the new
personality, because we want the new personality to affect the starting
of the new environment, but at the same time we do _not_ want the new
personality to take effect if flushing the old one fails.
As a result, the x86-64 '32-bit' personality is actually done using this
insane "I'm going to change the ABI, but I haven't done it yet" bit
(TIF_ABI_PENDING), with SET_PERSONALITY() not actually setting the
personality, but just the "pending" bit, so that "flush_thread()" can do
the actual personality magic.
This patch in no way changes any of that insanity, but it does split the
'flush_old_exec()' function up into a preparatory part that can fail
(still called flush_old_exec()), and a new part that will actually set
up the new exec environment (setup_new_exec()). All callers are changed
to trivially comply with the new world order.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-01-29 09:14:42 +03:00
void setup_new_exec ( struct linux_binprm * bprm )
{
2017-07-19 01:25:27 +03:00
/*
* Once here , prepare_binrpm ( ) will not be called any more , so
* the final state of setuid / setgid / fscaps can be merged into the
* secureexec flag .
*/
bprm - > secureexec | = bprm - > cap_elevated ;
2017-07-19 01:25:35 +03:00
if ( bprm - > secureexec ) {
2017-07-19 01:25:36 +03:00
/* Make sure parent cannot signal privileged process. */
current - > pdeath_signal = 0 ;
2017-07-19 01:25:35 +03:00
/*
* For secureexec , reset the stack limit to sane default to
* avoid bad behavior from the prior rlimits . This has to
* happen before arch_pick_mmap_layout ( ) , which examines
* RLIMIT_STACK , but after the point of no return to avoid
2017-12-12 22:28:38 +03:00
* needing to clean up the change on failure .
2017-07-19 01:25:35 +03:00
*/
2018-04-11 02:35:01 +03:00
if ( bprm - > rlim_stack . rlim_cur > _STK_LIM )
bprm - > rlim_stack . rlim_cur = _STK_LIM ;
2017-07-19 01:25:35 +03:00
}
2018-04-11 02:35:01 +03:00
arch_pick_mmap_layout ( current - > mm , & bprm - > rlim_stack ) ;
2005-04-17 02:20:36 +04:00
current - > sas_ss_sp = current - > sas_ss_size = 0 ;
2018-01-03 02:21:33 +03:00
/*
* Figure out dumpability . Note that this checking only of current
* is wrong , but userspace depends on it . This should be testing
* bprm - > secureexec instead .
*/
2017-07-19 01:25:34 +03:00
if ( bprm - > interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP | |
2018-01-03 02:21:33 +03:00
! ( uid_eq ( current_euid ( ) , current_uid ( ) ) & &
gid_eq ( current_egid ( ) , current_gid ( ) ) ) )
2007-07-19 12:48:27 +04:00
set_dumpable ( current - > mm , suid_dumpable ) ;
2017-07-19 01:25:34 +03:00
else
set_dumpable ( current - > mm , SUID_DUMP_USER ) ;
2005-06-23 11:09:43 +04:00
2017-03-20 11:16:26 +03:00
arch_setup_new_exec ( ) ;
2014-05-21 19:32:19 +04:00
perf_event_exec ( ) ;
2014-05-28 12:45:04 +04:00
__set_task_comm ( current , kbasename ( bprm - > filename ) , true ) ;
2005-04-17 02:20:36 +04:00
2006-03-01 03:59:19 +03:00
/* Set the new mm task size. We have to do that late because it may
* depend on TIF_32BIT which is only updated in flush_thread ( ) on
* some architectures like powerpc
*/
current - > mm - > task_size = TASK_SIZE ;
2005-04-17 02:20:36 +04:00
/* An exec changes our domain. We are no longer part of the thread
group */
current - > self_exec_id + + ;
flush_signal_handlers ( current , 0 ) ;
}
Split 'flush_old_exec' into two functions
'flush_old_exec()' is the point of no return when doing an execve(), and
it is pretty badly misnamed. It doesn't just flush the old executable
environment, it also starts up the new one.
Which is very inconvenient for things like setting up the new
personality, because we want the new personality to affect the starting
of the new environment, but at the same time we do _not_ want the new
personality to take effect if flushing the old one fails.
As a result, the x86-64 '32-bit' personality is actually done using this
insane "I'm going to change the ABI, but I haven't done it yet" bit
(TIF_ABI_PENDING), with SET_PERSONALITY() not actually setting the
personality, but just the "pending" bit, so that "flush_thread()" can do
the actual personality magic.
This patch in no way changes any of that insanity, but it does split the
'flush_old_exec()' function up into a preparatory part that can fail
(still called flush_old_exec()), and a new part that will actually set
up the new exec environment (setup_new_exec()). All callers are changed
to trivially comply with the new world order.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-01-29 09:14:42 +03:00
EXPORT_SYMBOL ( setup_new_exec ) ;
2005-04-17 02:20:36 +04:00
2018-04-11 02:34:57 +03:00
/* Runs immediately before start_thread() takes over. */
void finalize_exec ( struct linux_binprm * bprm )
{
2018-04-11 02:35:01 +03:00
/* Store any stack rlimit changes before starting thread. */
task_lock ( current - > group_leader ) ;
current - > signal - > rlim [ RLIMIT_STACK ] = bprm - > rlim_stack ;
task_unlock ( current - > group_leader ) ;
2018-04-11 02:34:57 +03:00
}
EXPORT_SYMBOL ( finalize_exec ) ;
2009-09-05 22:17:13 +04:00
/*
* Prepare credentials and lock - > cred_guard_mutex .
* install_exec_creds ( ) commits the new creds and drops the lock .
* Or , if exec fails before , free_bprm ( ) should release - > cred and
* and unlock .
*/
2018-12-10 10:49:54 +03:00
static int prepare_bprm_creds ( struct linux_binprm * bprm )
2009-09-05 22:17:13 +04:00
{
2010-10-28 02:34:08 +04:00
if ( mutex_lock_interruptible ( & current - > signal - > cred_guard_mutex ) )
2009-09-05 22:17:13 +04:00
return - ERESTARTNOINTR ;
bprm - > cred = prepare_exec_creds ( ) ;
if ( likely ( bprm - > cred ) )
return 0 ;
2010-10-28 02:34:08 +04:00
mutex_unlock ( & current - > signal - > cred_guard_mutex ) ;
2009-09-05 22:17:13 +04:00
return - ENOMEM ;
}
2014-02-06 00:54:53 +04:00
static void free_bprm ( struct linux_binprm * bprm )
2009-09-05 22:17:13 +04:00
{
free_arg_pages ( bprm ) ;
if ( bprm - > cred ) {
2010-10-28 02:34:08 +04:00
mutex_unlock ( & current - > signal - > cred_guard_mutex ) ;
2009-09-05 22:17:13 +04:00
abort_creds ( bprm - > cred ) ;
}
2014-01-24 03:55:51 +04:00
if ( bprm - > file ) {
allow_write_access ( bprm - > file ) ;
fput ( bprm - > file ) ;
}
exec: do not leave bprm->interp on stack
If a series of scripts are executed, each triggering module loading via
unprintable bytes in the script header, kernel stack contents can leak
into the command line.
Normally execution of binfmt_script and binfmt_misc happens recursively.
However, when modules are enabled, and unprintable bytes exist in the
bprm->buf, execution will restart after attempting to load matching
binfmt modules. Unfortunately, the logic in binfmt_script and
binfmt_misc does not expect to get restarted. They leave bprm->interp
pointing to their local stack. This means on restart bprm->interp is
left pointing into unused stack memory which can then be copied into the
userspace argv areas.
After additional study, it seems that both recursion and restart remains
the desirable way to handle exec with scripts, misc, and modules. As
such, we need to protect the changes to interp.
This changes the logic to require allocation for any changes to the
bprm->interp. To avoid adding a new kmalloc to every exec, the default
value is left as-is. Only when passing through binfmt_script or
binfmt_misc does an allocation take place.
For a proof of concept, see DoTest.sh from:
http://www.halfdog.net/Security/2012/LinuxKernelBinfmtScriptStackDataDisclosure/
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: halfdog <me@halfdog.net>
Cc: P J P <ppandit@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-12-21 03:05:16 +04:00
/* If a binfmt changed the interp, free it. */
if ( bprm - > interp ! = bprm - > filename )
kfree ( bprm - > interp ) ;
2009-09-05 22:17:13 +04:00
kfree ( bprm ) ;
}
2017-10-04 02:15:42 +03:00
int bprm_change_interp ( const char * interp , struct linux_binprm * bprm )
exec: do not leave bprm->interp on stack
If a series of scripts are executed, each triggering module loading via
unprintable bytes in the script header, kernel stack contents can leak
into the command line.
Normally execution of binfmt_script and binfmt_misc happens recursively.
However, when modules are enabled, and unprintable bytes exist in the
bprm->buf, execution will restart after attempting to load matching
binfmt modules. Unfortunately, the logic in binfmt_script and
binfmt_misc does not expect to get restarted. They leave bprm->interp
pointing to their local stack. This means on restart bprm->interp is
left pointing into unused stack memory which can then be copied into the
userspace argv areas.
After additional study, it seems that both recursion and restart remains
the desirable way to handle exec with scripts, misc, and modules. As
such, we need to protect the changes to interp.
This changes the logic to require allocation for any changes to the
bprm->interp. To avoid adding a new kmalloc to every exec, the default
value is left as-is. Only when passing through binfmt_script or
binfmt_misc does an allocation take place.
For a proof of concept, see DoTest.sh from:
http://www.halfdog.net/Security/2012/LinuxKernelBinfmtScriptStackDataDisclosure/
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: halfdog <me@halfdog.net>
Cc: P J P <ppandit@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-12-21 03:05:16 +04:00
{
/* If a binfmt changed the interp, free it first. */
if ( bprm - > interp ! = bprm - > filename )
kfree ( bprm - > interp ) ;
bprm - > interp = kstrdup ( interp , GFP_KERNEL ) ;
if ( ! bprm - > interp )
return - ENOMEM ;
return 0 ;
}
EXPORT_SYMBOL ( bprm_change_interp ) ;
CRED: Make execve() take advantage of copy-on-write credentials
Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.
I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).
The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.
(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.
This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.
(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.
(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.
(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.
This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.
(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.
(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:
(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().
(ii) Clear any bits in current->personality that were deferred from
(c.i).
(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:
(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.
This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).
(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.
(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.
(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.
(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.
(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.
(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()
Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().
(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.
(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()
New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.
The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.
(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 02:39:24 +03:00
/*
* install the new credentials for this executable
*/
void install_exec_creds ( struct linux_binprm * bprm )
{
security_bprm_committing_creds ( bprm ) ;
commit_creds ( bprm - > cred ) ;
bprm - > cred = NULL ;
2013-06-20 13:36:28 +04:00
/*
* Disable monitoring for regular users
* when executing setuid binaries . Must
* wait until new credentials are committed
* by commit_creds ( ) above
*/
if ( get_dumpable ( current - > mm ) ! = SUID_DUMP_USER )
perf_event_exit_task ( current ) ;
2009-09-05 22:17:13 +04:00
/*
* cred_guard_mutex must be held at least to this point to prevent
CRED: Make execve() take advantage of copy-on-write credentials
Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.
I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).
The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.
(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.
This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.
(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.
(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.
(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.
This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.
(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.
(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:
(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().
(ii) Clear any bits in current->personality that were deferred from
(c.i).
(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:
(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.
This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).
(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.
(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.
(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.
(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.
(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.
(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()
Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().
(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.
(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()
New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.
The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.
(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 02:39:24 +03:00
* ptrace_attach ( ) from altering our determination of the task ' s
2009-09-05 22:17:13 +04:00
* credentials ; any time after this it may be unlocked .
*/
CRED: Make execve() take advantage of copy-on-write credentials
Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.
I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).
The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.
(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.
This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.
(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.
(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.
(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.
This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.
(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.
(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:
(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().
(ii) Clear any bits in current->personality that were deferred from
(c.i).
(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:
(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.
This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).
(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.
(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.
(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.
(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.
(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.
(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()
Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().
(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.
(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()
New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.
The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.
(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 02:39:24 +03:00
security_bprm_committed_creds ( bprm ) ;
2010-10-28 02:34:08 +04:00
mutex_unlock ( & current - > signal - > cred_guard_mutex ) ;
CRED: Make execve() take advantage of copy-on-write credentials
Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.
I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).
The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.
(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.
This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.
(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.
(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.
(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.
This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.
(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.
(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:
(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().
(ii) Clear any bits in current->personality that were deferred from
(c.i).
(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:
(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.
This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).
(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.
(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.
(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.
(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.
(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.
(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()
Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().
(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.
(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()
New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.
The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.
(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 02:39:24 +03:00
}
EXPORT_SYMBOL ( install_exec_creds ) ;
/*
* determine how safe it is to execute the proposed program
2010-10-28 02:34:08 +04:00
* - the caller must hold - > cred_guard_mutex to protect against
2014-06-05 11:23:17 +04:00
* PTRACE_ATTACH or seccomp thread - sync
CRED: Make execve() take advantage of copy-on-write credentials
Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.
I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).
The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.
(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.
This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.
(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.
(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.
(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.
This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.
(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.
(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:
(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().
(ii) Clear any bits in current->personality that were deferred from
(c.i).
(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:
(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.
This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).
(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.
(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.
(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.
(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.
(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.
(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()
Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().
(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.
(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()
New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.
The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.
(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 02:39:24 +03:00
*/
2014-01-24 03:55:50 +04:00
static void check_unsafe_exec ( struct linux_binprm * bprm )
CRED: Make execve() take advantage of copy-on-write credentials
Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.
I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).
The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.
(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.
This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.
(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.
(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.
(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.
This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.
(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.
(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:
(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().
(ii) Clear any bits in current->personality that were deferred from
(c.i).
(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:
(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.
This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).
(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.
(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.
(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.
(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.
(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.
(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()
Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().
(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.
(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()
New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.
The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.
(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 02:39:24 +03:00
{
CRED: Fix SUID exec regression
The patch:
commit a6f76f23d297f70e2a6b3ec607f7aeeea9e37e8d
CRED: Make execve() take advantage of copy-on-write credentials
moved the place in which the 'safeness' of a SUID/SGID exec was performed to
before de_thread() was called. This means that LSM_UNSAFE_SHARE is now
calculated incorrectly. This flag is set if any of the usage counts for
fs_struct, files_struct and sighand_struct are greater than 1 at the time the
determination is made. All of which are true for threads created by the
pthread library.
However, since we wish to make the security calculation before irrevocably
damaging the process so that we can return it an error code in the case where
we decide we want to reject the exec request on this basis, we have to make the
determination before calling de_thread().
So, instead, we count up the number of threads (CLONE_THREAD) that are sharing
our fs_struct (CLONE_FS), files_struct (CLONE_FILES) and sighand_structs
(CLONE_SIGHAND/CLONE_THREAD) with us. These will be killed by de_thread() and
so can be discounted by check_unsafe_exec().
We do have to be careful because CLONE_THREAD does not imply FS or FILES.
We _assume_ that there will be no extra references to these structs held by the
threads we're going to kill.
This can be tested with the attached pair of programs. Build the two programs
using the Makefile supplied, and run ./test1 as a non-root user. If
successful, you should see something like:
[dhowells@andromeda tmp]$ ./test1
--TEST1--
uid=4043, euid=4043 suid=4043
exec ./test2
--TEST2--
uid=4043, euid=0 suid=0
SUCCESS - Correct effective user ID
and if unsuccessful, something like:
[dhowells@andromeda tmp]$ ./test1
--TEST1--
uid=4043, euid=4043 suid=4043
exec ./test2
--TEST2--
uid=4043, euid=4043 suid=4043
ERROR - Incorrect effective user ID!
The non-root user ID you see will depend on the user you run as.
[test1.c]
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
static void *thread_func(void *arg)
{
while (1) {}
}
int main(int argc, char **argv)
{
pthread_t tid;
uid_t uid, euid, suid;
printf("--TEST1--\n");
getresuid(&uid, &euid, &suid);
printf("uid=%d, euid=%d suid=%d\n", uid, euid, suid);
if (pthread_create(&tid, NULL, thread_func, NULL) < 0) {
perror("pthread_create");
exit(1);
}
printf("exec ./test2\n");
execlp("./test2", "test2", NULL);
perror("./test2");
_exit(1);
}
[test2.c]
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int main(int argc, char **argv)
{
uid_t uid, euid, suid;
getresuid(&uid, &euid, &suid);
printf("--TEST2--\n");
printf("uid=%d, euid=%d suid=%d\n", uid, euid, suid);
if (euid != 0) {
fprintf(stderr, "ERROR - Incorrect effective user ID!\n");
exit(1);
}
printf("SUCCESS - Correct effective user ID\n");
exit(0);
}
[Makefile]
CFLAGS = -D_GNU_SOURCE -Wall -Werror -Wunused
all: test1 test2
test1: test1.c
gcc $(CFLAGS) -o test1 test1.c -lpthread
test2: test2.c
gcc $(CFLAGS) -o test2 test2.c
sudo chown root.root test2
sudo chmod +s test2
Reported-by: David Smith <dsmith@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: David Smith <dsmith@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
2009-02-06 14:45:46 +03:00
struct task_struct * p = current , * t ;
2009-03-30 15:35:18 +04:00
unsigned n_fs ;
CRED: Make execve() take advantage of copy-on-write credentials
Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.
I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).
The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.
(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.
This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.
(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.
(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.
(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.
This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.
(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.
(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:
(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().
(ii) Clear any bits in current->personality that were deferred from
(c.i).
(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:
(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.
This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).
(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.
(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.
(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.
(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.
(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.
(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()
Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().
(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.
(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()
New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.
The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.
(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 02:39:24 +03:00
2017-01-23 07:26:31 +03:00
if ( p - > ptrace )
bprm - > unsafe | = LSM_UNSAFE_PTRACE ;
CRED: Make execve() take advantage of copy-on-write credentials
Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.
I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).
The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.
(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.
This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.
(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.
(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.
(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.
This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.
(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.
(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:
(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().
(ii) Clear any bits in current->personality that were deferred from
(c.i).
(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:
(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.
This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).
(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.
(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.
(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.
(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.
(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.
(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()
Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().
(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.
(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()
New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.
The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.
(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 02:39:24 +03:00
Add PR_{GET,SET}_NO_NEW_PRIVS to prevent execve from granting privs
With this change, calling
prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)
disables privilege granting operations at execve-time. For example, a
process will not be able to execute a setuid binary to change their uid
or gid if this bit is set. The same is true for file capabilities.
Additionally, LSM_UNSAFE_NO_NEW_PRIVS is defined to ensure that
LSMs respect the requested behavior.
To determine if the NO_NEW_PRIVS bit is set, a task may call
prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0);
It returns 1 if set and 0 if it is not set. If any of the arguments are
non-zero, it will return -1 and set errno to -EINVAL.
(PR_SET_NO_NEW_PRIVS behaves similarly.)
This functionality is desired for the proposed seccomp filter patch
series. By using PR_SET_NO_NEW_PRIVS, it allows a task to modify the
system call behavior for itself and its child tasks without being
able to impact the behavior of a more privileged task.
Another potential use is making certain privileged operations
unprivileged. For example, chroot may be considered "safe" if it cannot
affect privileged tasks.
Note, this patch causes execve to fail when PR_SET_NO_NEW_PRIVS is
set and AppArmor is in use. It is fixed in a subsequent patch.
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Will Drewry <wad@chromium.org>
Acked-by: Eric Paris <eparis@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
v18: updated change desc
v17: using new define values as per 3.4
Signed-off-by: James Morris <james.l.morris@oracle.com>
2012-04-13 01:47:50 +04:00
/*
* This isn ' t strictly necessary , but it makes it harder for LSMs to
* mess up .
*/
2014-05-22 02:23:46 +04:00
if ( task_no_new_privs ( current ) )
Add PR_{GET,SET}_NO_NEW_PRIVS to prevent execve from granting privs
With this change, calling
prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)
disables privilege granting operations at execve-time. For example, a
process will not be able to execute a setuid binary to change their uid
or gid if this bit is set. The same is true for file capabilities.
Additionally, LSM_UNSAFE_NO_NEW_PRIVS is defined to ensure that
LSMs respect the requested behavior.
To determine if the NO_NEW_PRIVS bit is set, a task may call
prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0);
It returns 1 if set and 0 if it is not set. If any of the arguments are
non-zero, it will return -1 and set errno to -EINVAL.
(PR_SET_NO_NEW_PRIVS behaves similarly.)
This functionality is desired for the proposed seccomp filter patch
series. By using PR_SET_NO_NEW_PRIVS, it allows a task to modify the
system call behavior for itself and its child tasks without being
able to impact the behavior of a more privileged task.
Another potential use is making certain privileged operations
unprivileged. For example, chroot may be considered "safe" if it cannot
affect privileged tasks.
Note, this patch causes execve to fail when PR_SET_NO_NEW_PRIVS is
set and AppArmor is in use. It is fixed in a subsequent patch.
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Will Drewry <wad@chromium.org>
Acked-by: Eric Paris <eparis@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
v18: updated change desc
v17: using new define values as per 3.4
Signed-off-by: James Morris <james.l.morris@oracle.com>
2012-04-13 01:47:50 +04:00
bprm - > unsafe | = LSM_UNSAFE_NO_NEW_PRIVS ;
2014-01-24 03:55:49 +04:00
t = p ;
CRED: Fix SUID exec regression
The patch:
commit a6f76f23d297f70e2a6b3ec607f7aeeea9e37e8d
CRED: Make execve() take advantage of copy-on-write credentials
moved the place in which the 'safeness' of a SUID/SGID exec was performed to
before de_thread() was called. This means that LSM_UNSAFE_SHARE is now
calculated incorrectly. This flag is set if any of the usage counts for
fs_struct, files_struct and sighand_struct are greater than 1 at the time the
determination is made. All of which are true for threads created by the
pthread library.
However, since we wish to make the security calculation before irrevocably
damaging the process so that we can return it an error code in the case where
we decide we want to reject the exec request on this basis, we have to make the
determination before calling de_thread().
So, instead, we count up the number of threads (CLONE_THREAD) that are sharing
our fs_struct (CLONE_FS), files_struct (CLONE_FILES) and sighand_structs
(CLONE_SIGHAND/CLONE_THREAD) with us. These will be killed by de_thread() and
so can be discounted by check_unsafe_exec().
We do have to be careful because CLONE_THREAD does not imply FS or FILES.
We _assume_ that there will be no extra references to these structs held by the
threads we're going to kill.
This can be tested with the attached pair of programs. Build the two programs
using the Makefile supplied, and run ./test1 as a non-root user. If
successful, you should see something like:
[dhowells@andromeda tmp]$ ./test1
--TEST1--
uid=4043, euid=4043 suid=4043
exec ./test2
--TEST2--
uid=4043, euid=0 suid=0
SUCCESS - Correct effective user ID
and if unsuccessful, something like:
[dhowells@andromeda tmp]$ ./test1
--TEST1--
uid=4043, euid=4043 suid=4043
exec ./test2
--TEST2--
uid=4043, euid=4043 suid=4043
ERROR - Incorrect effective user ID!
The non-root user ID you see will depend on the user you run as.
[test1.c]
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
static void *thread_func(void *arg)
{
while (1) {}
}
int main(int argc, char **argv)
{
pthread_t tid;
uid_t uid, euid, suid;
printf("--TEST1--\n");
getresuid(&uid, &euid, &suid);
printf("uid=%d, euid=%d suid=%d\n", uid, euid, suid);
if (pthread_create(&tid, NULL, thread_func, NULL) < 0) {
perror("pthread_create");
exit(1);
}
printf("exec ./test2\n");
execlp("./test2", "test2", NULL);
perror("./test2");
_exit(1);
}
[test2.c]
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int main(int argc, char **argv)
{
uid_t uid, euid, suid;
getresuid(&uid, &euid, &suid);
printf("--TEST2--\n");
printf("uid=%d, euid=%d suid=%d\n", uid, euid, suid);
if (euid != 0) {
fprintf(stderr, "ERROR - Incorrect effective user ID!\n");
exit(1);
}
printf("SUCCESS - Correct effective user ID\n");
exit(0);
}
[Makefile]
CFLAGS = -D_GNU_SOURCE -Wall -Werror -Wunused
all: test1 test2
test1: test1.c
gcc $(CFLAGS) -o test1 test1.c -lpthread
test2: test2.c
gcc $(CFLAGS) -o test2 test2.c
sudo chown root.root test2
sudo chmod +s test2
Reported-by: David Smith <dsmith@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: David Smith <dsmith@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
2009-02-06 14:45:46 +03:00
n_fs = 1 ;
2010-08-17 22:37:33 +04:00
spin_lock ( & p - > fs - > lock ) ;
2009-04-24 03:02:45 +04:00
rcu_read_lock ( ) ;
2014-01-24 03:55:49 +04:00
while_each_thread ( p , t ) {
CRED: Fix SUID exec regression
The patch:
commit a6f76f23d297f70e2a6b3ec607f7aeeea9e37e8d
CRED: Make execve() take advantage of copy-on-write credentials
moved the place in which the 'safeness' of a SUID/SGID exec was performed to
before de_thread() was called. This means that LSM_UNSAFE_SHARE is now
calculated incorrectly. This flag is set if any of the usage counts for
fs_struct, files_struct and sighand_struct are greater than 1 at the time the
determination is made. All of which are true for threads created by the
pthread library.
However, since we wish to make the security calculation before irrevocably
damaging the process so that we can return it an error code in the case where
we decide we want to reject the exec request on this basis, we have to make the
determination before calling de_thread().
So, instead, we count up the number of threads (CLONE_THREAD) that are sharing
our fs_struct (CLONE_FS), files_struct (CLONE_FILES) and sighand_structs
(CLONE_SIGHAND/CLONE_THREAD) with us. These will be killed by de_thread() and
so can be discounted by check_unsafe_exec().
We do have to be careful because CLONE_THREAD does not imply FS or FILES.
We _assume_ that there will be no extra references to these structs held by the
threads we're going to kill.
This can be tested with the attached pair of programs. Build the two programs
using the Makefile supplied, and run ./test1 as a non-root user. If
successful, you should see something like:
[dhowells@andromeda tmp]$ ./test1
--TEST1--
uid=4043, euid=4043 suid=4043
exec ./test2
--TEST2--
uid=4043, euid=0 suid=0
SUCCESS - Correct effective user ID
and if unsuccessful, something like:
[dhowells@andromeda tmp]$ ./test1
--TEST1--
uid=4043, euid=4043 suid=4043
exec ./test2
--TEST2--
uid=4043, euid=4043 suid=4043
ERROR - Incorrect effective user ID!
The non-root user ID you see will depend on the user you run as.
[test1.c]
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
static void *thread_func(void *arg)
{
while (1) {}
}
int main(int argc, char **argv)
{
pthread_t tid;
uid_t uid, euid, suid;
printf("--TEST1--\n");
getresuid(&uid, &euid, &suid);
printf("uid=%d, euid=%d suid=%d\n", uid, euid, suid);
if (pthread_create(&tid, NULL, thread_func, NULL) < 0) {
perror("pthread_create");
exit(1);
}
printf("exec ./test2\n");
execlp("./test2", "test2", NULL);
perror("./test2");
_exit(1);
}
[test2.c]
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int main(int argc, char **argv)
{
uid_t uid, euid, suid;
getresuid(&uid, &euid, &suid);
printf("--TEST2--\n");
printf("uid=%d, euid=%d suid=%d\n", uid, euid, suid);
if (euid != 0) {
fprintf(stderr, "ERROR - Incorrect effective user ID!\n");
exit(1);
}
printf("SUCCESS - Correct effective user ID\n");
exit(0);
}
[Makefile]
CFLAGS = -D_GNU_SOURCE -Wall -Werror -Wunused
all: test1 test2
test1: test1.c
gcc $(CFLAGS) -o test1 test1.c -lpthread
test2: test2.c
gcc $(CFLAGS) -o test2 test2.c
sudo chown root.root test2
sudo chmod +s test2
Reported-by: David Smith <dsmith@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: David Smith <dsmith@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
2009-02-06 14:45:46 +03:00
if ( t - > fs = = p - > fs )
n_fs + + ;
}
2009-04-24 03:02:45 +04:00
rcu_read_unlock ( ) ;
CRED: Fix SUID exec regression
The patch:
commit a6f76f23d297f70e2a6b3ec607f7aeeea9e37e8d
CRED: Make execve() take advantage of copy-on-write credentials
moved the place in which the 'safeness' of a SUID/SGID exec was performed to
before de_thread() was called. This means that LSM_UNSAFE_SHARE is now
calculated incorrectly. This flag is set if any of the usage counts for
fs_struct, files_struct and sighand_struct are greater than 1 at the time the
determination is made. All of which are true for threads created by the
pthread library.
However, since we wish to make the security calculation before irrevocably
damaging the process so that we can return it an error code in the case where
we decide we want to reject the exec request on this basis, we have to make the
determination before calling de_thread().
So, instead, we count up the number of threads (CLONE_THREAD) that are sharing
our fs_struct (CLONE_FS), files_struct (CLONE_FILES) and sighand_structs
(CLONE_SIGHAND/CLONE_THREAD) with us. These will be killed by de_thread() and
so can be discounted by check_unsafe_exec().
We do have to be careful because CLONE_THREAD does not imply FS or FILES.
We _assume_ that there will be no extra references to these structs held by the
threads we're going to kill.
This can be tested with the attached pair of programs. Build the two programs
using the Makefile supplied, and run ./test1 as a non-root user. If
successful, you should see something like:
[dhowells@andromeda tmp]$ ./test1
--TEST1--
uid=4043, euid=4043 suid=4043
exec ./test2
--TEST2--
uid=4043, euid=0 suid=0
SUCCESS - Correct effective user ID
and if unsuccessful, something like:
[dhowells@andromeda tmp]$ ./test1
--TEST1--
uid=4043, euid=4043 suid=4043
exec ./test2
--TEST2--
uid=4043, euid=4043 suid=4043
ERROR - Incorrect effective user ID!
The non-root user ID you see will depend on the user you run as.
[test1.c]
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
static void *thread_func(void *arg)
{
while (1) {}
}
int main(int argc, char **argv)
{
pthread_t tid;
uid_t uid, euid, suid;
printf("--TEST1--\n");
getresuid(&uid, &euid, &suid);
printf("uid=%d, euid=%d suid=%d\n", uid, euid, suid);
if (pthread_create(&tid, NULL, thread_func, NULL) < 0) {
perror("pthread_create");
exit(1);
}
printf("exec ./test2\n");
execlp("./test2", "test2", NULL);
perror("./test2");
_exit(1);
}
[test2.c]
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int main(int argc, char **argv)
{
uid_t uid, euid, suid;
getresuid(&uid, &euid, &suid);
printf("--TEST2--\n");
printf("uid=%d, euid=%d suid=%d\n", uid, euid, suid);
if (euid != 0) {
fprintf(stderr, "ERROR - Incorrect effective user ID!\n");
exit(1);
}
printf("SUCCESS - Correct effective user ID\n");
exit(0);
}
[Makefile]
CFLAGS = -D_GNU_SOURCE -Wall -Werror -Wunused
all: test1 test2
test1: test1.c
gcc $(CFLAGS) -o test1 test1.c -lpthread
test2: test2.c
gcc $(CFLAGS) -o test2 test2.c
sudo chown root.root test2
sudo chmod +s test2
Reported-by: David Smith <dsmith@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: David Smith <dsmith@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
2009-02-06 14:45:46 +03:00
2014-01-24 03:55:50 +04:00
if ( p - > fs - > users > n_fs )
CRED: Make execve() take advantage of copy-on-write credentials
Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.
I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).
The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.
(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.
This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.
(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.
(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.
(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.
This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.
(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.
(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:
(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().
(ii) Clear any bits in current->personality that were deferred from
(c.i).
(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:
(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.
This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).
(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.
(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.
(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.
(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.
(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.
(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()
Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().
(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.
(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()
New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.
The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.
(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 02:39:24 +03:00
bprm - > unsafe | = LSM_UNSAFE_SHARE ;
2014-01-24 03:55:50 +04:00
else
p - > fs - > in_exec = 1 ;
2010-08-17 22:37:33 +04:00
spin_unlock ( & p - > fs - > lock ) ;
CRED: Make execve() take advantage of copy-on-write credentials
Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.
I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).
The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.
(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.
This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.
(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.
(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.
(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.
This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.
(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.
(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:
(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().
(ii) Clear any bits in current->personality that were deferred from
(c.i).
(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:
(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.
This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).
(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.
(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.
(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.
(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.
(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.
(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()
Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().
(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.
(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()
New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.
The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.
(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 02:39:24 +03:00
}
2015-04-19 03:48:39 +03:00
static void bprm_fill_uid ( struct linux_binprm * bprm )
{
struct inode * inode ;
unsigned int mode ;
kuid_t uid ;
kgid_t gid ;
2016-05-17 22:14:39 +03:00
/*
* Since this can be called multiple times ( via prepare_binprm ) ,
* we must clear any previous work done when setting set [ ug ] id
* bits from any earlier bprm - > file uses ( for example when run
* first for a setuid script then again for its interpreter ) .
*/
2015-04-19 03:48:39 +03:00
bprm - > cred - > euid = current_euid ( ) ;
bprm - > cred - > egid = current_egid ( ) ;
fs: Treat foreign mounts as nosuid
If a process gets access to a mount from a different user
namespace, that process should not be able to take advantage of
setuid files or selinux entrypoints from that filesystem. Prevent
this by treating mounts from other mount namespaces and those not
owned by current_user_ns() or an ancestor as nosuid.
This will make it safer to allow more complex filesystems to be
mounted in non-root user namespaces.
This does not remove the need for MNT_LOCK_NOSUID. The setuid,
setgid, and file capability bits can no longer be abused if code in
a user namespace were to clear nosuid on an untrusted filesystem,
but this patch, by itself, is insufficient to protect the system
from abuse of files that, when execed, would increase MAC privilege.
As a more concrete explanation, any task that can manipulate a
vfsmount associated with a given user namespace already has
capabilities in that namespace and all of its descendents. If they
can cause a malicious setuid, setgid, or file-caps executable to
appear in that mount, then that executable will only allow them to
elevate privileges in exactly the set of namespaces in which they
are already privileges.
On the other hand, if they can cause a malicious executable to
appear with a dangerous MAC label, running it could change the
caller's security context in a way that should not have been
possible, even inside the namespace in which the task is confined.
As a hardening measure, this would have made CVE-2014-5207 much
more difficult to exploit.
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Acked-by: James Morris <james.l.morris@oracle.com>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2016-06-24 00:41:05 +03:00
if ( ! mnt_may_suid ( bprm - > file - > f_path . mnt ) )
2015-04-19 03:48:39 +03:00
return ;
if ( task_no_new_privs ( current ) )
return ;
2017-02-13 23:45:26 +03:00
inode = bprm - > file - > f_path . dentry - > d_inode ;
2015-04-19 03:48:39 +03:00
mode = READ_ONCE ( inode - > i_mode ) ;
if ( ! ( mode & ( S_ISUID | S_ISGID ) ) )
return ;
/* Be careful if suid/sgid is set */
2016-01-22 23:40:57 +03:00
inode_lock ( inode ) ;
2015-04-19 03:48:39 +03:00
/* reload atomically mode/uid/gid now that lock held */
mode = inode - > i_mode ;
uid = inode - > i_uid ;
gid = inode - > i_gid ;
2016-01-22 23:40:57 +03:00
inode_unlock ( inode ) ;
2015-04-19 03:48:39 +03:00
/* We ignore suid/sgid if there are no mappings for them in the ns */
if ( ! kuid_has_mapping ( bprm - > cred - > user_ns , uid ) | |
! kgid_has_mapping ( bprm - > cred - > user_ns , gid ) )
return ;
if ( mode & S_ISUID ) {
bprm - > per_clear | = PER_CLEAR_ON_SETID ;
bprm - > cred - > euid = uid ;
}
if ( ( mode & ( S_ISGID | S_IXGRP ) ) = = ( S_ISGID | S_IXGRP ) ) {
bprm - > per_clear | = PER_CLEAR_ON_SETID ;
bprm - > cred - > egid = gid ;
}
}
2014-01-24 03:55:50 +04:00
/*
* Fill the binprm structure from the inode .
2019-03-08 03:29:26 +03:00
* Check permissions , then read the first BINPRM_BUF_SIZE bytes
CRED: Make execve() take advantage of copy-on-write credentials
Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.
I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).
The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.
(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.
This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.
(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.
(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.
(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.
This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.
(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.
(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:
(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().
(ii) Clear any bits in current->personality that were deferred from
(c.i).
(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:
(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.
This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).
(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.
(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.
(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.
(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.
(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.
(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()
Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().
(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.
(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()
New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.
The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.
(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 02:39:24 +03:00
*
* This may be called multiple times for binary chains ( scripts for example ) .
2005-04-17 02:20:36 +04:00
*/
int prepare_binprm ( struct linux_binprm * bprm )
{
int retval ;
2017-09-01 18:39:13 +03:00
loff_t pos = 0 ;
2005-04-17 02:20:36 +04:00
2015-04-19 03:48:39 +03:00
bprm_fill_uid ( bprm ) ;
2005-04-17 02:20:36 +04:00
/* fill in binprm security blob */
CRED: Make execve() take advantage of copy-on-write credentials
Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.
I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).
The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.
(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.
This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.
(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.
(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.
(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.
This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.
(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.
(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:
(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().
(ii) Clear any bits in current->personality that were deferred from
(c.i).
(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:
(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.
This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).
(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.
(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.
(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.
(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.
(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.
(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()
Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().
(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.
(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()
New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.
The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.
(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 02:39:24 +03:00
retval = security_bprm_set_creds ( bprm ) ;
2005-04-17 02:20:36 +04:00
if ( retval )
return retval ;
2017-07-19 01:25:23 +03:00
bprm - > called_set_creds = 1 ;
2005-04-17 02:20:36 +04:00
CRED: Make execve() take advantage of copy-on-write credentials
Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.
I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).
The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.
(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.
This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.
(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.
(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.
(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.
This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.
(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.
(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:
(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().
(ii) Clear any bits in current->personality that were deferred from
(c.i).
(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:
(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.
This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).
(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.
(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.
(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.
(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.
(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.
(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()
Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().
(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.
(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()
New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.
The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.
(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 02:39:24 +03:00
memset ( bprm - > buf , 0 , BINPRM_BUF_SIZE ) ;
2017-09-01 18:39:13 +03:00
return kernel_read ( bprm - > file , bprm - > buf , BINPRM_BUF_SIZE , & pos ) ;
2005-04-17 02:20:36 +04:00
}
EXPORT_SYMBOL ( prepare_binprm ) ;
2007-05-08 11:25:16 +04:00
/*
* Arguments are ' \0 ' separated strings found at the location bprm - > p
* points to ; chop off the first by relocating brpm - > p to right after
* the first ' \0 ' encountered .
*/
2007-07-19 12:48:16 +04:00
int remove_arg_zero ( struct linux_binprm * bprm )
2005-04-17 02:20:36 +04:00
{
2007-07-19 12:48:16 +04:00
int ret = 0 ;
unsigned long offset ;
char * kaddr ;
struct page * page ;
2007-05-08 11:25:16 +04:00
2007-07-19 12:48:16 +04:00
if ( ! bprm - > argc )
return 0 ;
2005-04-17 02:20:36 +04:00
2007-07-19 12:48:16 +04:00
do {
offset = bprm - > p & ~ PAGE_MASK ;
page = get_arg_page ( bprm , bprm - > p , 0 ) ;
if ( ! page ) {
ret = - EFAULT ;
goto out ;
}
2011-11-25 19:14:27 +04:00
kaddr = kmap_atomic ( page ) ;
2007-05-08 11:25:16 +04:00
2007-07-19 12:48:16 +04:00
for ( ; offset < PAGE_SIZE & & kaddr [ offset ] ;
offset + + , bprm - > p + + )
;
2007-05-08 11:25:16 +04:00
2011-11-25 19:14:27 +04:00
kunmap_atomic ( kaddr ) ;
2007-07-19 12:48:16 +04:00
put_arg_page ( page ) ;
} while ( offset = = PAGE_SIZE ) ;
2007-05-08 11:25:16 +04:00
2007-07-19 12:48:16 +04:00
bprm - > p + + ;
bprm - > argc - - ;
ret = 0 ;
2007-05-08 11:25:16 +04:00
2007-07-19 12:48:16 +04:00
out :
return ret ;
2005-04-17 02:20:36 +04:00
}
EXPORT_SYMBOL ( remove_arg_zero ) ;
2013-09-12 01:24:44 +04:00
# define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
2005-04-17 02:20:36 +04:00
/*
* cycle the list of binary formats handler , until one recognizes the image
*/
2012-10-21 05:53:31 +04:00
int search_binary_handler ( struct linux_binprm * bprm )
2005-04-17 02:20:36 +04:00
{
2013-09-12 01:24:44 +04:00
bool need_retry = IS_ENABLED ( CONFIG_MODULES ) ;
2005-04-17 02:20:36 +04:00
struct linux_binfmt * fmt ;
2013-09-12 01:24:44 +04:00
int retval ;
2005-04-17 02:20:36 +04:00
2012-12-18 04:03:20 +04:00
/* This allows 4 levels of binfmt rewrites before failing hard. */
2013-09-12 01:24:39 +04:00
if ( bprm - > recursion_depth > 5 )
2012-12-18 04:03:20 +04:00
return - ELOOP ;
2005-04-17 02:20:36 +04:00
retval = security_bprm_check ( bprm ) ;
if ( retval )
return retval ;
retval = - ENOENT ;
2013-09-12 01:24:44 +04:00
retry :
read_lock ( & binfmt_lock ) ;
list_for_each_entry ( fmt , & formats , lh ) {
if ( ! try_module_get ( fmt - > module ) )
continue ;
read_unlock ( & binfmt_lock ) ;
2019-05-15 01:44:37 +03:00
2013-09-12 01:24:44 +04:00
bprm - > recursion_depth + + ;
retval = fmt - > load_binary ( bprm ) ;
2019-05-15 01:44:37 +03:00
bprm - > recursion_depth - - ;
2014-05-05 04:11:36 +04:00
read_lock ( & binfmt_lock ) ;
put_binfmt ( fmt ) ;
if ( retval < 0 & & ! bprm - > mm ) {
/* we got to flush_old_exec() and failed after it */
read_unlock ( & binfmt_lock ) ;
2019-05-21 18:03:48 +03:00
force_sigsegv ( SIGSEGV ) ;
2014-05-05 04:11:36 +04:00
return retval ;
}
if ( retval ! = - ENOEXEC | | ! bprm - > file ) {
read_unlock ( & binfmt_lock ) ;
2013-09-12 01:24:44 +04:00
return retval ;
2005-04-17 02:20:36 +04:00
}
}
2013-09-12 01:24:44 +04:00
read_unlock ( & binfmt_lock ) ;
2014-05-05 04:11:36 +04:00
if ( need_retry ) {
2013-09-12 01:24:44 +04:00
if ( printable ( bprm - > buf [ 0 ] ) & & printable ( bprm - > buf [ 1 ] ) & &
printable ( bprm - > buf [ 2 ] ) & & printable ( bprm - > buf [ 3 ] ) )
return retval ;
2013-09-12 01:24:45 +04:00
if ( request_module ( " binfmt-%04x " , * ( ushort * ) ( bprm - > buf + 2 ) ) < 0 )
return retval ;
2013-09-12 01:24:44 +04:00
need_retry = false ;
goto retry ;
}
2005-04-17 02:20:36 +04:00
return retval ;
}
EXPORT_SYMBOL ( search_binary_handler ) ;
2013-09-12 01:24:38 +04:00
static int exec_binprm ( struct linux_binprm * bprm )
{
pid_t old_pid , old_vpid ;
int ret ;
/* Need to fetch pid before load_binary changes it */
old_pid = current - > pid ;
rcu_read_lock ( ) ;
old_vpid = task_pid_nr_ns ( current , task_active_pid_ns ( current - > parent ) ) ;
rcu_read_unlock ( ) ;
ret = search_binary_handler ( bprm ) ;
if ( ret > = 0 ) {
2013-11-22 07:18:14 +04:00
audit_bprm ( bprm ) ;
2013-09-12 01:24:38 +04:00
trace_sched_process_exec ( current , old_pid , bprm ) ;
ptrace_event ( PTRACE_EVENT_EXEC , old_vpid ) ;
2013-09-12 01:24:40 +04:00
proc_exec_connector ( current ) ;
2013-09-12 01:24:38 +04:00
}
return ret ;
}
2005-04-17 02:20:36 +04:00
/*
* sys_execve ( ) executes a new program .
*/
umh: introduce fork_usermode_blob() helper
Introduce helper:
int fork_usermode_blob(void *data, size_t len, struct umh_info *info);
struct umh_info {
struct file *pipe_to_umh;
struct file *pipe_from_umh;
pid_t pid;
};
that GPLed kernel modules (signed or unsigned) can use it to execute part
of its own data as swappable user mode process.
The kernel will do:
- allocate a unique file in tmpfs
- populate that file with [data, data + len] bytes
- user-mode-helper code will do_execve that file and, before the process
starts, the kernel will create two unix pipes for bidirectional
communication between kernel module and umh
- close tmpfs file, effectively deleting it
- the fork_usermode_blob will return zero on success and populate
'struct umh_info' with two unix pipes and the pid of the user process
As the first step in the development of the bpfilter project
the fork_usermode_blob() helper is introduced to allow user mode code
to be invoked from a kernel module. The idea is that user mode code plus
normal kernel module code are built as part of the kernel build
and installed as traditional kernel module into distro specified location,
such that from a distribution point of view, there is
no difference between regular kernel modules and kernel modules + umh code.
Such modules can be signed, modprobed, rmmod, etc. The use of this new helper
by a kernel module doesn't make it any special from kernel and user space
tooling point of view.
Such approach enables kernel to delegate functionality traditionally done
by the kernel modules into the user space processes (either root or !root) and
reduces security attack surface of the new code. The buggy umh code would crash
the user process, but not the kernel. Another advantage is that umh code
of the kernel module can be debugged and tested out of user space
(e.g. opening the possibility to run clang sanitizers, fuzzers or
user space test suites on the umh code).
In case of the bpfilter project such architecture allows complex control plane
to be done in the user space while bpf based data plane stays in the kernel.
Since umh can crash, can be oom-ed by the kernel, killed by the admin,
the kernel module that uses them (like bpfilter) needs to manage life
time of umh on its own via two unix pipes and the pid of umh.
The exit code of such kernel module should kill the umh it started,
so that rmmod of the kernel module will cleanup the corresponding umh.
Just like if the kernel module does kmalloc() it should kfree() it
in the exit code.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-05-22 05:22:29 +03:00
static int __do_execve_file ( int fd , struct filename * filename ,
struct user_arg_ptr argv ,
struct user_arg_ptr envp ,
int flags , struct file * file )
2005-04-17 02:20:36 +04:00
{
syscalls: implement execveat() system call
This patchset adds execveat(2) for x86, and is derived from Meredydd
Luff's patch from Sept 2012 (https://lkml.org/lkml/2012/9/11/528).
The primary aim of adding an execveat syscall is to allow an
implementation of fexecve(3) that does not rely on the /proc filesystem,
at least for executables (rather than scripts). The current glibc version
of fexecve(3) is implemented via /proc, which causes problems in sandboxed
or otherwise restricted environments.
Given the desire for a /proc-free fexecve() implementation, HPA suggested
(https://lkml.org/lkml/2006/7/11/556) that an execveat(2) syscall would be
an appropriate generalization.
Also, having a new syscall means that it can take a flags argument without
back-compatibility concerns. The current implementation just defines the
AT_EMPTY_PATH and AT_SYMLINK_NOFOLLOW flags, but other flags could be
added in future -- for example, flags for new namespaces (as suggested at
https://lkml.org/lkml/2006/7/11/474).
Related history:
- https://lkml.org/lkml/2006/12/27/123 is an example of someone
realizing that fexecve() is likely to fail in a chroot environment.
- http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043 covered
documenting the /proc requirement of fexecve(3) in its manpage, to
"prevent other people from wasting their time".
- https://bugzilla.redhat.com/show_bug.cgi?id=241609 described a
problem where a process that did setuid() could not fexecve()
because it no longer had access to /proc/self/fd; this has since
been fixed.
This patch (of 4):
Add a new execveat(2) system call. execveat() is to execve() as openat()
is to open(): it takes a file descriptor that refers to a directory, and
resolves the filename relative to that.
In addition, if the filename is empty and AT_EMPTY_PATH is specified,
execveat() executes the file to which the file descriptor refers. This
replicates the functionality of fexecve(), which is a system call in other
UNIXen, but in Linux glibc it depends on opening "/proc/self/fd/<fd>" (and
so relies on /proc being mounted).
The filename fed to the executed program as argv[0] (or the name of the
script fed to a script interpreter) will be of the form "/dev/fd/<fd>"
(for an empty filename) or "/dev/fd/<fd>/<filename>", effectively
reflecting how the executable was found. This does however mean that
execution of a script in a /proc-less environment won't work; also, script
execution via an O_CLOEXEC file descriptor fails (as the file will not be
accessible after exec).
Based on patches by Meredydd Luff.
Signed-off-by: David Drysdale <drysdale@google.com>
Cc: Meredydd Luff <meredydd@senatehouse.org>
Cc: Shuah Khan <shuah.kh@samsung.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rich Felker <dalias@aerifal.cx>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-13 03:57:29 +03:00
char * pathbuf = NULL ;
2005-04-17 02:20:36 +04:00
struct linux_binprm * bprm ;
2008-04-22 13:31:30 +04:00
struct files_struct * displaced ;
2005-04-17 02:20:36 +04:00
int retval ;
2011-08-08 19:02:04 +04:00
2014-02-06 00:54:53 +04:00
if ( IS_ERR ( filename ) )
return PTR_ERR ( filename ) ;
2011-08-08 19:02:04 +04:00
/*
* We move the actual failure in case of RLIMIT_NPROC excess from
* set * uid ( ) to execve ( ) because too many poorly written programs
* don ' t check setuid ( ) return code . Here we additionally recheck
* whether NPROC limit is still exceeded .
*/
if ( ( current - > flags & PF_NPROC_EXCEEDED ) & &
2013-07-04 02:08:34 +04:00
atomic_read ( & current_user ( ) - > processes ) > rlimit ( RLIMIT_NPROC ) ) {
2011-08-08 19:02:04 +04:00
retval = - EAGAIN ;
goto out_ret ;
}
/* We're below the limit (still or again), so we don't want to make
* further execve ( ) calls fail . */
current - > flags & = ~ PF_NPROC_EXCEEDED ;
2005-04-17 02:20:36 +04:00
2008-04-22 13:31:30 +04:00
retval = unshare_files ( & displaced ) ;
2008-04-22 13:11:59 +04:00
if ( retval )
goto out_ret ;
2005-04-17 02:20:36 +04:00
retval = - ENOMEM ;
2006-03-25 14:08:13 +03:00
bprm = kzalloc ( sizeof ( * bprm ) , GFP_KERNEL ) ;
2005-04-17 02:20:36 +04:00
if ( ! bprm )
2008-04-22 13:11:59 +04:00
goto out_files ;
2005-04-17 02:20:36 +04:00
2009-09-05 22:17:13 +04:00
retval = prepare_bprm_creds ( bprm ) ;
if ( retval )
CRED: Make execve() take advantage of copy-on-write credentials
Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.
I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).
The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.
(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.
This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.
(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.
(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.
(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.
This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.
(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.
(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:
(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().
(ii) Clear any bits in current->personality that were deferred from
(c.i).
(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:
(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.
This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).
(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.
(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.
(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.
(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.
(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.
(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()
Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().
(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.
(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()
New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.
The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.
(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 02:39:24 +03:00
goto out_free ;
2009-03-30 15:20:30 +04:00
2014-01-24 03:55:50 +04:00
check_unsafe_exec ( bprm ) ;
2009-09-05 22:17:13 +04:00
current - > in_execve = 1 ;
CRED: Make execve() take advantage of copy-on-write credentials
Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.
I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).
The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.
(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.
This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.
(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.
(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.
(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.
This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.
(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.
(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:
(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().
(ii) Clear any bits in current->personality that were deferred from
(c.i).
(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:
(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.
This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).
(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.
(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.
(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.
(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.
(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.
(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()
Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().
(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.
(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()
New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.
The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.
(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 02:39:24 +03:00
umh: introduce fork_usermode_blob() helper
Introduce helper:
int fork_usermode_blob(void *data, size_t len, struct umh_info *info);
struct umh_info {
struct file *pipe_to_umh;
struct file *pipe_from_umh;
pid_t pid;
};
that GPLed kernel modules (signed or unsigned) can use it to execute part
of its own data as swappable user mode process.
The kernel will do:
- allocate a unique file in tmpfs
- populate that file with [data, data + len] bytes
- user-mode-helper code will do_execve that file and, before the process
starts, the kernel will create two unix pipes for bidirectional
communication between kernel module and umh
- close tmpfs file, effectively deleting it
- the fork_usermode_blob will return zero on success and populate
'struct umh_info' with two unix pipes and the pid of the user process
As the first step in the development of the bpfilter project
the fork_usermode_blob() helper is introduced to allow user mode code
to be invoked from a kernel module. The idea is that user mode code plus
normal kernel module code are built as part of the kernel build
and installed as traditional kernel module into distro specified location,
such that from a distribution point of view, there is
no difference between regular kernel modules and kernel modules + umh code.
Such modules can be signed, modprobed, rmmod, etc. The use of this new helper
by a kernel module doesn't make it any special from kernel and user space
tooling point of view.
Such approach enables kernel to delegate functionality traditionally done
by the kernel modules into the user space processes (either root or !root) and
reduces security attack surface of the new code. The buggy umh code would crash
the user process, but not the kernel. Another advantage is that umh code
of the kernel module can be debugged and tested out of user space
(e.g. opening the possibility to run clang sanitizers, fuzzers or
user space test suites on the umh code).
In case of the bpfilter project such architecture allows complex control plane
to be done in the user space while bpf based data plane stays in the kernel.
Since umh can crash, can be oom-ed by the kernel, killed by the admin,
the kernel module that uses them (like bpfilter) needs to manage life
time of umh on its own via two unix pipes and the pid of umh.
The exit code of such kernel module should kill the umh it started,
so that rmmod of the kernel module will cleanup the corresponding umh.
Just like if the kernel module does kmalloc() it should kfree() it
in the exit code.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-05-22 05:22:29 +03:00
if ( ! file )
file = do_open_execat ( fd , filename , flags ) ;
2005-04-17 02:20:36 +04:00
retval = PTR_ERR ( file ) ;
if ( IS_ERR ( file ) )
2009-03-30 15:20:30 +04:00
goto out_unmark ;
2005-04-17 02:20:36 +04:00
sched_exec ( ) ;
bprm - > file = file ;
umh: introduce fork_usermode_blob() helper
Introduce helper:
int fork_usermode_blob(void *data, size_t len, struct umh_info *info);
struct umh_info {
struct file *pipe_to_umh;
struct file *pipe_from_umh;
pid_t pid;
};
that GPLed kernel modules (signed or unsigned) can use it to execute part
of its own data as swappable user mode process.
The kernel will do:
- allocate a unique file in tmpfs
- populate that file with [data, data + len] bytes
- user-mode-helper code will do_execve that file and, before the process
starts, the kernel will create two unix pipes for bidirectional
communication between kernel module and umh
- close tmpfs file, effectively deleting it
- the fork_usermode_blob will return zero on success and populate
'struct umh_info' with two unix pipes and the pid of the user process
As the first step in the development of the bpfilter project
the fork_usermode_blob() helper is introduced to allow user mode code
to be invoked from a kernel module. The idea is that user mode code plus
normal kernel module code are built as part of the kernel build
and installed as traditional kernel module into distro specified location,
such that from a distribution point of view, there is
no difference between regular kernel modules and kernel modules + umh code.
Such modules can be signed, modprobed, rmmod, etc. The use of this new helper
by a kernel module doesn't make it any special from kernel and user space
tooling point of view.
Such approach enables kernel to delegate functionality traditionally done
by the kernel modules into the user space processes (either root or !root) and
reduces security attack surface of the new code. The buggy umh code would crash
the user process, but not the kernel. Another advantage is that umh code
of the kernel module can be debugged and tested out of user space
(e.g. opening the possibility to run clang sanitizers, fuzzers or
user space test suites on the umh code).
In case of the bpfilter project such architecture allows complex control plane
to be done in the user space while bpf based data plane stays in the kernel.
Since umh can crash, can be oom-ed by the kernel, killed by the admin,
the kernel module that uses them (like bpfilter) needs to manage life
time of umh on its own via two unix pipes and the pid of umh.
The exit code of such kernel module should kill the umh it started,
so that rmmod of the kernel module will cleanup the corresponding umh.
Just like if the kernel module does kmalloc() it should kfree() it
in the exit code.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-05-22 05:22:29 +03:00
if ( ! filename ) {
bprm - > filename = " none " ;
} else if ( fd = = AT_FDCWD | | filename - > name [ 0 ] = = ' / ' ) {
syscalls: implement execveat() system call
This patchset adds execveat(2) for x86, and is derived from Meredydd
Luff's patch from Sept 2012 (https://lkml.org/lkml/2012/9/11/528).
The primary aim of adding an execveat syscall is to allow an
implementation of fexecve(3) that does not rely on the /proc filesystem,
at least for executables (rather than scripts). The current glibc version
of fexecve(3) is implemented via /proc, which causes problems in sandboxed
or otherwise restricted environments.
Given the desire for a /proc-free fexecve() implementation, HPA suggested
(https://lkml.org/lkml/2006/7/11/556) that an execveat(2) syscall would be
an appropriate generalization.
Also, having a new syscall means that it can take a flags argument without
back-compatibility concerns. The current implementation just defines the
AT_EMPTY_PATH and AT_SYMLINK_NOFOLLOW flags, but other flags could be
added in future -- for example, flags for new namespaces (as suggested at
https://lkml.org/lkml/2006/7/11/474).
Related history:
- https://lkml.org/lkml/2006/12/27/123 is an example of someone
realizing that fexecve() is likely to fail in a chroot environment.
- http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043 covered
documenting the /proc requirement of fexecve(3) in its manpage, to
"prevent other people from wasting their time".
- https://bugzilla.redhat.com/show_bug.cgi?id=241609 described a
problem where a process that did setuid() could not fexecve()
because it no longer had access to /proc/self/fd; this has since
been fixed.
This patch (of 4):
Add a new execveat(2) system call. execveat() is to execve() as openat()
is to open(): it takes a file descriptor that refers to a directory, and
resolves the filename relative to that.
In addition, if the filename is empty and AT_EMPTY_PATH is specified,
execveat() executes the file to which the file descriptor refers. This
replicates the functionality of fexecve(), which is a system call in other
UNIXen, but in Linux glibc it depends on opening "/proc/self/fd/<fd>" (and
so relies on /proc being mounted).
The filename fed to the executed program as argv[0] (or the name of the
script fed to a script interpreter) will be of the form "/dev/fd/<fd>"
(for an empty filename) or "/dev/fd/<fd>/<filename>", effectively
reflecting how the executable was found. This does however mean that
execution of a script in a /proc-less environment won't work; also, script
execution via an O_CLOEXEC file descriptor fails (as the file will not be
accessible after exec).
Based on patches by Meredydd Luff.
Signed-off-by: David Drysdale <drysdale@google.com>
Cc: Meredydd Luff <meredydd@senatehouse.org>
Cc: Shuah Khan <shuah.kh@samsung.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rich Felker <dalias@aerifal.cx>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-13 03:57:29 +03:00
bprm - > filename = filename - > name ;
} else {
if ( filename - > name [ 0 ] = = ' \0 ' )
2017-09-14 02:28:29 +03:00
pathbuf = kasprintf ( GFP_KERNEL , " /dev/fd/%d " , fd ) ;
syscalls: implement execveat() system call
This patchset adds execveat(2) for x86, and is derived from Meredydd
Luff's patch from Sept 2012 (https://lkml.org/lkml/2012/9/11/528).
The primary aim of adding an execveat syscall is to allow an
implementation of fexecve(3) that does not rely on the /proc filesystem,
at least for executables (rather than scripts). The current glibc version
of fexecve(3) is implemented via /proc, which causes problems in sandboxed
or otherwise restricted environments.
Given the desire for a /proc-free fexecve() implementation, HPA suggested
(https://lkml.org/lkml/2006/7/11/556) that an execveat(2) syscall would be
an appropriate generalization.
Also, having a new syscall means that it can take a flags argument without
back-compatibility concerns. The current implementation just defines the
AT_EMPTY_PATH and AT_SYMLINK_NOFOLLOW flags, but other flags could be
added in future -- for example, flags for new namespaces (as suggested at
https://lkml.org/lkml/2006/7/11/474).
Related history:
- https://lkml.org/lkml/2006/12/27/123 is an example of someone
realizing that fexecve() is likely to fail in a chroot environment.
- http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043 covered
documenting the /proc requirement of fexecve(3) in its manpage, to
"prevent other people from wasting their time".
- https://bugzilla.redhat.com/show_bug.cgi?id=241609 described a
problem where a process that did setuid() could not fexecve()
because it no longer had access to /proc/self/fd; this has since
been fixed.
This patch (of 4):
Add a new execveat(2) system call. execveat() is to execve() as openat()
is to open(): it takes a file descriptor that refers to a directory, and
resolves the filename relative to that.
In addition, if the filename is empty and AT_EMPTY_PATH is specified,
execveat() executes the file to which the file descriptor refers. This
replicates the functionality of fexecve(), which is a system call in other
UNIXen, but in Linux glibc it depends on opening "/proc/self/fd/<fd>" (and
so relies on /proc being mounted).
The filename fed to the executed program as argv[0] (or the name of the
script fed to a script interpreter) will be of the form "/dev/fd/<fd>"
(for an empty filename) or "/dev/fd/<fd>/<filename>", effectively
reflecting how the executable was found. This does however mean that
execution of a script in a /proc-less environment won't work; also, script
execution via an O_CLOEXEC file descriptor fails (as the file will not be
accessible after exec).
Based on patches by Meredydd Luff.
Signed-off-by: David Drysdale <drysdale@google.com>
Cc: Meredydd Luff <meredydd@senatehouse.org>
Cc: Shuah Khan <shuah.kh@samsung.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rich Felker <dalias@aerifal.cx>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-13 03:57:29 +03:00
else
2017-09-14 02:28:29 +03:00
pathbuf = kasprintf ( GFP_KERNEL , " /dev/fd/%d/%s " ,
syscalls: implement execveat() system call
This patchset adds execveat(2) for x86, and is derived from Meredydd
Luff's patch from Sept 2012 (https://lkml.org/lkml/2012/9/11/528).
The primary aim of adding an execveat syscall is to allow an
implementation of fexecve(3) that does not rely on the /proc filesystem,
at least for executables (rather than scripts). The current glibc version
of fexecve(3) is implemented via /proc, which causes problems in sandboxed
or otherwise restricted environments.
Given the desire for a /proc-free fexecve() implementation, HPA suggested
(https://lkml.org/lkml/2006/7/11/556) that an execveat(2) syscall would be
an appropriate generalization.
Also, having a new syscall means that it can take a flags argument without
back-compatibility concerns. The current implementation just defines the
AT_EMPTY_PATH and AT_SYMLINK_NOFOLLOW flags, but other flags could be
added in future -- for example, flags for new namespaces (as suggested at
https://lkml.org/lkml/2006/7/11/474).
Related history:
- https://lkml.org/lkml/2006/12/27/123 is an example of someone
realizing that fexecve() is likely to fail in a chroot environment.
- http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043 covered
documenting the /proc requirement of fexecve(3) in its manpage, to
"prevent other people from wasting their time".
- https://bugzilla.redhat.com/show_bug.cgi?id=241609 described a
problem where a process that did setuid() could not fexecve()
because it no longer had access to /proc/self/fd; this has since
been fixed.
This patch (of 4):
Add a new execveat(2) system call. execveat() is to execve() as openat()
is to open(): it takes a file descriptor that refers to a directory, and
resolves the filename relative to that.
In addition, if the filename is empty and AT_EMPTY_PATH is specified,
execveat() executes the file to which the file descriptor refers. This
replicates the functionality of fexecve(), which is a system call in other
UNIXen, but in Linux glibc it depends on opening "/proc/self/fd/<fd>" (and
so relies on /proc being mounted).
The filename fed to the executed program as argv[0] (or the name of the
script fed to a script interpreter) will be of the form "/dev/fd/<fd>"
(for an empty filename) or "/dev/fd/<fd>/<filename>", effectively
reflecting how the executable was found. This does however mean that
execution of a script in a /proc-less environment won't work; also, script
execution via an O_CLOEXEC file descriptor fails (as the file will not be
accessible after exec).
Based on patches by Meredydd Luff.
Signed-off-by: David Drysdale <drysdale@google.com>
Cc: Meredydd Luff <meredydd@senatehouse.org>
Cc: Shuah Khan <shuah.kh@samsung.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rich Felker <dalias@aerifal.cx>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-13 03:57:29 +03:00
fd , filename - > name ) ;
if ( ! pathbuf ) {
retval = - ENOMEM ;
goto out_unmark ;
}
/*
* Record that a name derived from an O_CLOEXEC fd will be
* inaccessible after exec . Relies on having exclusive access to
* current - > files ( due to unshare_files above ) .
*/
if ( close_on_exec ( fd , rcu_dereference_raw ( current - > files - > fdt ) ) )
bprm - > interp_flags | = BINPRM_FLAGS_PATH_INACCESSIBLE ;
bprm - > filename = pathbuf ;
}
bprm - > interp = bprm - > filename ;
2005-04-17 02:20:36 +04:00
2007-07-19 12:48:16 +04:00
retval = bprm_mm_init ( bprm ) ;
if ( retval )
2014-01-24 03:55:51 +04:00
goto out_unmark ;
2005-04-17 02:20:36 +04:00
2019-01-04 02:28:11 +03:00
retval = prepare_arg_pages ( bprm , argv , envp ) ;
if ( retval < 0 )
2005-04-17 02:20:36 +04:00
goto out ;
retval = prepare_binprm ( bprm ) ;
if ( retval < 0 )
goto out ;
retval = copy_strings_kernel ( 1 , & bprm - > filename , bprm ) ;
if ( retval < 0 )
goto out ;
bprm - > exec = bprm - > p ;
retval = copy_strings ( bprm - > envc , envp , bprm ) ;
if ( retval < 0 )
goto out ;
retval = copy_strings ( bprm - > argc , argv , bprm ) ;
if ( retval < 0 )
goto out ;
2016-11-17 07:06:51 +03:00
would_dump ( bprm , bprm - > file ) ;
2013-09-12 01:24:38 +04:00
retval = exec_binprm ( bprm ) ;
CRED: Make execve() take advantage of copy-on-write credentials
Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.
I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).
The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.
(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.
This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.
(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.
(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.
(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.
This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.
(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.
(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:
(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().
(ii) Clear any bits in current->personality that were deferred from
(c.i).
(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:
(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.
This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).
(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.
(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.
(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.
(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.
(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.
(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()
Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().
(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.
(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()
New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.
The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.
(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 02:39:24 +03:00
if ( retval < 0 )
goto out ;
2005-04-17 02:20:36 +04:00
CRED: Make execve() take advantage of copy-on-write credentials
Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.
I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).
The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.
(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.
This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.
(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.
(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.
(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.
This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.
(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.
(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:
(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().
(ii) Clear any bits in current->personality that were deferred from
(c.i).
(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:
(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.
This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).
(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.
(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.
(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.
(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.
(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.
(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()
Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().
(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.
(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()
New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.
The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.
(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 02:39:24 +03:00
/* execve succeeded */
2009-03-30 15:20:30 +04:00
current - > fs - > in_exec = 0 ;
2009-02-05 11:18:11 +03:00
current - > in_execve = 0 ;
rseq: Introduce restartable sequences system call
Expose a new system call allowing each thread to register one userspace
memory area to be used as an ABI between kernel and user-space for two
purposes: user-space restartable sequences and quick access to read the
current CPU number value from user-space.
* Restartable sequences (per-cpu atomics)
Restartables sequences allow user-space to perform update operations on
per-cpu data without requiring heavy-weight atomic operations.
The restartable critical sections (percpu atomics) work has been started
by Paul Turner and Andrew Hunter. It lets the kernel handle restart of
critical sections. [1] [2] The re-implementation proposed here brings a
few simplifications to the ABI which facilitates porting to other
architectures and speeds up the user-space fast path.
Here are benchmarks of various rseq use-cases.
Test hardware:
arm32: ARMv7 Processor rev 4 (v7l) "Cubietruck", 2-core
x86-64: Intel E5-2630 v3@2.40GHz, 16-core, hyperthreading
The following benchmarks were all performed on a single thread.
* Per-CPU statistic counter increment
getcpu+atomic (ns/op) rseq (ns/op) speedup
arm32: 344.0 31.4 11.0
x86-64: 15.3 2.0 7.7
* LTTng-UST: write event 32-bit header, 32-bit payload into tracer
per-cpu buffer
getcpu+atomic (ns/op) rseq (ns/op) speedup
arm32: 2502.0 2250.0 1.1
x86-64: 117.4 98.0 1.2
* liburcu percpu: lock-unlock pair, dereference, read/compare word
getcpu+atomic (ns/op) rseq (ns/op) speedup
arm32: 751.0 128.5 5.8
x86-64: 53.4 28.6 1.9
* jemalloc memory allocator adapted to use rseq
Using rseq with per-cpu memory pools in jemalloc at Facebook (based on
rseq 2016 implementation):
The production workload response-time has 1-2% gain avg. latency, and
the P99 overall latency drops by 2-3%.
* Reading the current CPU number
Speeding up reading the current CPU number on which the caller thread is
running is done by keeping the current CPU number up do date within the
cpu_id field of the memory area registered by the thread. This is done
by making scheduler preemption set the TIF_NOTIFY_RESUME flag on the
current thread. Upon return to user-space, a notify-resume handler
updates the current CPU value within the registered user-space memory
area. User-space can then read the current CPU number directly from
memory.
Keeping the current cpu id in a memory area shared between kernel and
user-space is an improvement over current mechanisms available to read
the current CPU number, which has the following benefits over
alternative approaches:
- 35x speedup on ARM vs system call through glibc
- 20x speedup on x86 compared to calling glibc, which calls vdso
executing a "lsl" instruction,
- 14x speedup on x86 compared to inlined "lsl" instruction,
- Unlike vdso approaches, this cpu_id value can be read from an inline
assembly, which makes it a useful building block for restartable
sequences.
- The approach of reading the cpu id through memory mapping shared
between kernel and user-space is portable (e.g. ARM), which is not the
case for the lsl-based x86 vdso.
On x86, yet another possible approach would be to use the gs segment
selector to point to user-space per-cpu data. This approach performs
similarly to the cpu id cache, but it has two disadvantages: it is
not portable, and it is incompatible with existing applications already
using the gs segment selector for other purposes.
Benchmarking various approaches for reading the current CPU number:
ARMv7 Processor rev 4 (v7l)
Machine model: Cubietruck
- Baseline (empty loop): 8.4 ns
- Read CPU from rseq cpu_id: 16.7 ns
- Read CPU from rseq cpu_id (lazy register): 19.8 ns
- glibc 2.19-0ubuntu6.6 getcpu: 301.8 ns
- getcpu system call: 234.9 ns
x86-64 Intel(R) Xeon(R) CPU E5-2630 v3 @ 2.40GHz:
- Baseline (empty loop): 0.8 ns
- Read CPU from rseq cpu_id: 0.8 ns
- Read CPU from rseq cpu_id (lazy register): 0.8 ns
- Read using gs segment selector: 0.8 ns
- "lsl" inline assembly: 13.0 ns
- glibc 2.19-0ubuntu6 getcpu: 16.6 ns
- getcpu system call: 53.9 ns
- Speed (benchmark taken on v8 of patchset)
Running 10 runs of hackbench -l 100000 seems to indicate, contrary to
expectations, that enabling CONFIG_RSEQ slightly accelerates the
scheduler:
Configuration: 2 sockets * 8-core Intel(R) Xeon(R) CPU E5-2630 v3 @
2.40GHz (directly on hardware, hyperthreading disabled in BIOS, energy
saving disabled in BIOS, turboboost disabled in BIOS, cpuidle.off=1
kernel parameter), with a Linux v4.6 defconfig+localyesconfig,
restartable sequences series applied.
* CONFIG_RSEQ=n
avg.: 41.37 s
std.dev.: 0.36 s
* CONFIG_RSEQ=y
avg.: 40.46 s
std.dev.: 0.33 s
- Size
On x86-64, between CONFIG_RSEQ=n/y, the text size increase of vmlinux is
567 bytes, and the data size increase of vmlinux is 5696 bytes.
[1] https://lwn.net/Articles/650333/
[2] http://www.linuxplumbersconf.org/2013/ocw/system/presentations/1695/original/LPC%20-%20PerCpu%20Atomics.pdf
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Watson <davejwatson@fb.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: Chris Lameter <cl@linux.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Andrew Hunter <ahh@google.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Paul Turner <pjt@google.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Maurer <bmaurer@fb.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-api@vger.kernel.org
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20151027235635.16059.11630.stgit@pjt-glaptop.roam.corp.google.com
Link: http://lkml.kernel.org/r/20150624222609.6116.86035.stgit@kitami.mtv.corp.google.com
Link: https://lkml.kernel.org/r/20180602124408.8430-3-mathieu.desnoyers@efficios.com
2018-06-02 15:43:54 +03:00
rseq_execve ( current ) ;
CRED: Make execve() take advantage of copy-on-write credentials
Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.
I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).
The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.
(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.
This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.
(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.
(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.
(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.
This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.
(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.
(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:
(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().
(ii) Clear any bits in current->personality that were deferred from
(c.i).
(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:
(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.
This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).
(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.
(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.
(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.
(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.
(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.
(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()
Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().
(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.
(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()
New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.
The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.
(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 02:39:24 +03:00
acct_update_integrals ( current ) ;
2019-07-16 18:20:45 +03:00
task_numa_free ( current , false ) ;
CRED: Make execve() take advantage of copy-on-write credentials
Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.
I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).
The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.
(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.
This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.
(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.
(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.
(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.
This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.
(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.
(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:
(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().
(ii) Clear any bits in current->personality that were deferred from
(c.i).
(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:
(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.
This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).
(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.
(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.
(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.
(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.
(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.
(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()
Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().
(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.
(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()
New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.
The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.
(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 02:39:24 +03:00
free_bprm ( bprm ) ;
syscalls: implement execveat() system call
This patchset adds execveat(2) for x86, and is derived from Meredydd
Luff's patch from Sept 2012 (https://lkml.org/lkml/2012/9/11/528).
The primary aim of adding an execveat syscall is to allow an
implementation of fexecve(3) that does not rely on the /proc filesystem,
at least for executables (rather than scripts). The current glibc version
of fexecve(3) is implemented via /proc, which causes problems in sandboxed
or otherwise restricted environments.
Given the desire for a /proc-free fexecve() implementation, HPA suggested
(https://lkml.org/lkml/2006/7/11/556) that an execveat(2) syscall would be
an appropriate generalization.
Also, having a new syscall means that it can take a flags argument without
back-compatibility concerns. The current implementation just defines the
AT_EMPTY_PATH and AT_SYMLINK_NOFOLLOW flags, but other flags could be
added in future -- for example, flags for new namespaces (as suggested at
https://lkml.org/lkml/2006/7/11/474).
Related history:
- https://lkml.org/lkml/2006/12/27/123 is an example of someone
realizing that fexecve() is likely to fail in a chroot environment.
- http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043 covered
documenting the /proc requirement of fexecve(3) in its manpage, to
"prevent other people from wasting their time".
- https://bugzilla.redhat.com/show_bug.cgi?id=241609 described a
problem where a process that did setuid() could not fexecve()
because it no longer had access to /proc/self/fd; this has since
been fixed.
This patch (of 4):
Add a new execveat(2) system call. execveat() is to execve() as openat()
is to open(): it takes a file descriptor that refers to a directory, and
resolves the filename relative to that.
In addition, if the filename is empty and AT_EMPTY_PATH is specified,
execveat() executes the file to which the file descriptor refers. This
replicates the functionality of fexecve(), which is a system call in other
UNIXen, but in Linux glibc it depends on opening "/proc/self/fd/<fd>" (and
so relies on /proc being mounted).
The filename fed to the executed program as argv[0] (or the name of the
script fed to a script interpreter) will be of the form "/dev/fd/<fd>"
(for an empty filename) or "/dev/fd/<fd>/<filename>", effectively
reflecting how the executable was found. This does however mean that
execution of a script in a /proc-less environment won't work; also, script
execution via an O_CLOEXEC file descriptor fails (as the file will not be
accessible after exec).
Based on patches by Meredydd Luff.
Signed-off-by: David Drysdale <drysdale@google.com>
Cc: Meredydd Luff <meredydd@senatehouse.org>
Cc: Shuah Khan <shuah.kh@samsung.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rich Felker <dalias@aerifal.cx>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-13 03:57:29 +03:00
kfree ( pathbuf ) ;
umh: introduce fork_usermode_blob() helper
Introduce helper:
int fork_usermode_blob(void *data, size_t len, struct umh_info *info);
struct umh_info {
struct file *pipe_to_umh;
struct file *pipe_from_umh;
pid_t pid;
};
that GPLed kernel modules (signed or unsigned) can use it to execute part
of its own data as swappable user mode process.
The kernel will do:
- allocate a unique file in tmpfs
- populate that file with [data, data + len] bytes
- user-mode-helper code will do_execve that file and, before the process
starts, the kernel will create two unix pipes for bidirectional
communication between kernel module and umh
- close tmpfs file, effectively deleting it
- the fork_usermode_blob will return zero on success and populate
'struct umh_info' with two unix pipes and the pid of the user process
As the first step in the development of the bpfilter project
the fork_usermode_blob() helper is introduced to allow user mode code
to be invoked from a kernel module. The idea is that user mode code plus
normal kernel module code are built as part of the kernel build
and installed as traditional kernel module into distro specified location,
such that from a distribution point of view, there is
no difference between regular kernel modules and kernel modules + umh code.
Such modules can be signed, modprobed, rmmod, etc. The use of this new helper
by a kernel module doesn't make it any special from kernel and user space
tooling point of view.
Such approach enables kernel to delegate functionality traditionally done
by the kernel modules into the user space processes (either root or !root) and
reduces security attack surface of the new code. The buggy umh code would crash
the user process, but not the kernel. Another advantage is that umh code
of the kernel module can be debugged and tested out of user space
(e.g. opening the possibility to run clang sanitizers, fuzzers or
user space test suites on the umh code).
In case of the bpfilter project such architecture allows complex control plane
to be done in the user space while bpf based data plane stays in the kernel.
Since umh can crash, can be oom-ed by the kernel, killed by the admin,
the kernel module that uses them (like bpfilter) needs to manage life
time of umh on its own via two unix pipes and the pid of umh.
The exit code of such kernel module should kill the umh it started,
so that rmmod of the kernel module will cleanup the corresponding umh.
Just like if the kernel module does kmalloc() it should kfree() it
in the exit code.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-05-22 05:22:29 +03:00
if ( filename )
putname ( filename ) ;
CRED: Make execve() take advantage of copy-on-write credentials
Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.
I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).
The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.
(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.
This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.
(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.
(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.
(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.
This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.
(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.
(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:
(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().
(ii) Clear any bits in current->personality that were deferred from
(c.i).
(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:
(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.
This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).
(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.
(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.
(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.
(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.
(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.
(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()
Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().
(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.
(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()
New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.
The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.
(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 02:39:24 +03:00
if ( displaced )
put_files_struct ( displaced ) ;
return retval ;
2005-04-17 02:20:36 +04:00
CRED: Make execve() take advantage of copy-on-write credentials
Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.
I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).
The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.
(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.
This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.
(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.
(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.
(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.
This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.
(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.
(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:
(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().
(ii) Clear any bits in current->personality that were deferred from
(c.i).
(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:
(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.
This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).
(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.
(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.
(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.
(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.
(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.
(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()
Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().
(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.
(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()
New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.
The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.
(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 02:39:24 +03:00
out :
2010-11-30 22:55:34 +03:00
if ( bprm - > mm ) {
acct_arg_size ( bprm , 0 ) ;
mmput ( bprm - > mm ) ;
}
2005-04-17 02:20:36 +04:00
2009-03-30 15:20:30 +04:00
out_unmark :
2014-01-24 03:55:50 +04:00
current - > fs - > in_exec = 0 ;
2009-02-05 11:18:11 +03:00
current - > in_execve = 0 ;
CRED: Make execve() take advantage of copy-on-write credentials
Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.
This patch and the preceding patches have been tested with the LTP SELinux
testsuite.
This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.
I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).
The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.
(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.
This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.
(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.
(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.
(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.
This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.
(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.
(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:
(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().
(ii) Clear any bits in current->personality that were deferred from
(c.i).
(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:
(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.
This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).
(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.
(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.
(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.
(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.
(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.
(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()
Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().
(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.
(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()
New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.
The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:
(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.
(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 02:39:24 +03:00
out_free :
2008-05-11 00:38:25 +04:00
free_bprm ( bprm ) ;
syscalls: implement execveat() system call
This patchset adds execveat(2) for x86, and is derived from Meredydd
Luff's patch from Sept 2012 (https://lkml.org/lkml/2012/9/11/528).
The primary aim of adding an execveat syscall is to allow an
implementation of fexecve(3) that does not rely on the /proc filesystem,
at least for executables (rather than scripts). The current glibc version
of fexecve(3) is implemented via /proc, which causes problems in sandboxed
or otherwise restricted environments.
Given the desire for a /proc-free fexecve() implementation, HPA suggested
(https://lkml.org/lkml/2006/7/11/556) that an execveat(2) syscall would be
an appropriate generalization.
Also, having a new syscall means that it can take a flags argument without
back-compatibility concerns. The current implementation just defines the
AT_EMPTY_PATH and AT_SYMLINK_NOFOLLOW flags, but other flags could be
added in future -- for example, flags for new namespaces (as suggested at
https://lkml.org/lkml/2006/7/11/474).
Related history:
- https://lkml.org/lkml/2006/12/27/123 is an example of someone
realizing that fexecve() is likely to fail in a chroot environment.
- http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043 covered
documenting the /proc requirement of fexecve(3) in its manpage, to
"prevent other people from wasting their time".
- https://bugzilla.redhat.com/show_bug.cgi?id=241609 described a
problem where a process that did setuid() could not fexecve()
because it no longer had access to /proc/self/fd; this has since
been fixed.
This patch (of 4):
Add a new execveat(2) system call. execveat() is to execve() as openat()
is to open(): it takes a file descriptor that refers to a directory, and
resolves the filename relative to that.
In addition, if the filename is empty and AT_EMPTY_PATH is specified,
execveat() executes the file to which the file descriptor refers. This
replicates the functionality of fexecve(), which is a system call in other
UNIXen, but in Linux glibc it depends on opening "/proc/self/fd/<fd>" (and
so relies on /proc being mounted).
The filename fed to the executed program as argv[0] (or the name of the
script fed to a script interpreter) will be of the form "/dev/fd/<fd>"
(for an empty filename) or "/dev/fd/<fd>/<filename>", effectively
reflecting how the executable was found. This does however mean that
execution of a script in a /proc-less environment won't work; also, script
execution via an O_CLOEXEC file descriptor fails (as the file will not be
accessible after exec).
Based on patches by Meredydd Luff.
Signed-off-by: David Drysdale <drysdale@google.com>
Cc: Meredydd Luff <meredydd@senatehouse.org>
Cc: Shuah Khan <shuah.kh@samsung.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rich Felker <dalias@aerifal.cx>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-13 03:57:29 +03:00
kfree ( pathbuf ) ;
2005-04-17 02:20:36 +04:00
2008-04-22 13:11:59 +04:00
out_files :
2008-04-22 13:31:30 +04:00
if ( displaced )
reset_files_struct ( displaced ) ;
2005-04-17 02:20:36 +04:00
out_ret :
umh: introduce fork_usermode_blob() helper
Introduce helper:
int fork_usermode_blob(void *data, size_t len, struct umh_info *info);
struct umh_info {
struct file *pipe_to_umh;
struct file *pipe_from_umh;
pid_t pid;
};
that GPLed kernel modules (signed or unsigned) can use it to execute part
of its own data as swappable user mode process.
The kernel will do:
- allocate a unique file in tmpfs
- populate that file with [data, data + len] bytes
- user-mode-helper code will do_execve that file and, before the process
starts, the kernel will create two unix pipes for bidirectional
communication between kernel module and umh
- close tmpfs file, effectively deleting it
- the fork_usermode_blob will return zero on success and populate
'struct umh_info' with two unix pipes and the pid of the user process
As the first step in the development of the bpfilter project
the fork_usermode_blob() helper is introduced to allow user mode code
to be invoked from a kernel module. The idea is that user mode code plus
normal kernel module code are built as part of the kernel build
and installed as traditional kernel module into distro specified location,
such that from a distribution point of view, there is
no difference between regular kernel modules and kernel modules + umh code.
Such modules can be signed, modprobed, rmmod, etc. The use of this new helper
by a kernel module doesn't make it any special from kernel and user space
tooling point of view.
Such approach enables kernel to delegate functionality traditionally done
by the kernel modules into the user space processes (either root or !root) and
reduces security attack surface of the new code. The buggy umh code would crash
the user process, but not the kernel. Another advantage is that umh code
of the kernel module can be debugged and tested out of user space
(e.g. opening the possibility to run clang sanitizers, fuzzers or
user space test suites on the umh code).
In case of the bpfilter project such architecture allows complex control plane
to be done in the user space while bpf based data plane stays in the kernel.
Since umh can crash, can be oom-ed by the kernel, killed by the admin,
the kernel module that uses them (like bpfilter) needs to manage life
time of umh on its own via two unix pipes and the pid of umh.
The exit code of such kernel module should kill the umh it started,
so that rmmod of the kernel module will cleanup the corresponding umh.
Just like if the kernel module does kmalloc() it should kfree() it
in the exit code.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-05-22 05:22:29 +03:00
if ( filename )
putname ( filename ) ;
2005-04-17 02:20:36 +04:00
return retval ;
}
umh: introduce fork_usermode_blob() helper
Introduce helper:
int fork_usermode_blob(void *data, size_t len, struct umh_info *info);
struct umh_info {
struct file *pipe_to_umh;
struct file *pipe_from_umh;
pid_t pid;
};
that GPLed kernel modules (signed or unsigned) can use it to execute part
of its own data as swappable user mode process.
The kernel will do:
- allocate a unique file in tmpfs
- populate that file with [data, data + len] bytes
- user-mode-helper code will do_execve that file and, before the process
starts, the kernel will create two unix pipes for bidirectional
communication between kernel module and umh
- close tmpfs file, effectively deleting it
- the fork_usermode_blob will return zero on success and populate
'struct umh_info' with two unix pipes and the pid of the user process
As the first step in the development of the bpfilter project
the fork_usermode_blob() helper is introduced to allow user mode code
to be invoked from a kernel module. The idea is that user mode code plus
normal kernel module code are built as part of the kernel build
and installed as traditional kernel module into distro specified location,
such that from a distribution point of view, there is
no difference between regular kernel modules and kernel modules + umh code.
Such modules can be signed, modprobed, rmmod, etc. The use of this new helper
by a kernel module doesn't make it any special from kernel and user space
tooling point of view.
Such approach enables kernel to delegate functionality traditionally done
by the kernel modules into the user space processes (either root or !root) and
reduces security attack surface of the new code. The buggy umh code would crash
the user process, but not the kernel. Another advantage is that umh code
of the kernel module can be debugged and tested out of user space
(e.g. opening the possibility to run clang sanitizers, fuzzers or
user space test suites on the umh code).
In case of the bpfilter project such architecture allows complex control plane
to be done in the user space while bpf based data plane stays in the kernel.
Since umh can crash, can be oom-ed by the kernel, killed by the admin,
the kernel module that uses them (like bpfilter) needs to manage life
time of umh on its own via two unix pipes and the pid of umh.
The exit code of such kernel module should kill the umh it started,
so that rmmod of the kernel module will cleanup the corresponding umh.
Just like if the kernel module does kmalloc() it should kfree() it
in the exit code.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-05-22 05:22:29 +03:00
static int do_execveat_common ( int fd , struct filename * filename ,
struct user_arg_ptr argv ,
struct user_arg_ptr envp ,
int flags )
{
return __do_execve_file ( fd , filename , argv , envp , flags , NULL ) ;
}
int do_execve_file ( struct file * file , void * __argv , void * __envp )
{
struct user_arg_ptr argv = { . ptr . native = __argv } ;
struct user_arg_ptr envp = { . ptr . native = __envp } ;
return __do_execve_file ( AT_FDCWD , NULL , argv , envp , 0 , file ) ;
}
2014-02-06 00:54:53 +04:00
int do_execve ( struct filename * filename ,
2011-03-06 20:02:37 +03:00
const char __user * const __user * __argv ,
2012-10-21 05:49:33 +04:00
const char __user * const __user * __envp )
2011-03-06 20:02:37 +03:00
{
2011-03-06 20:02:54 +03:00
struct user_arg_ptr argv = { . ptr . native = __argv } ;
struct user_arg_ptr envp = { . ptr . native = __envp } ;
syscalls: implement execveat() system call
This patchset adds execveat(2) for x86, and is derived from Meredydd
Luff's patch from Sept 2012 (https://lkml.org/lkml/2012/9/11/528).
The primary aim of adding an execveat syscall is to allow an
implementation of fexecve(3) that does not rely on the /proc filesystem,
at least for executables (rather than scripts). The current glibc version
of fexecve(3) is implemented via /proc, which causes problems in sandboxed
or otherwise restricted environments.
Given the desire for a /proc-free fexecve() implementation, HPA suggested
(https://lkml.org/lkml/2006/7/11/556) that an execveat(2) syscall would be
an appropriate generalization.
Also, having a new syscall means that it can take a flags argument without
back-compatibility concerns. The current implementation just defines the
AT_EMPTY_PATH and AT_SYMLINK_NOFOLLOW flags, but other flags could be
added in future -- for example, flags for new namespaces (as suggested at
https://lkml.org/lkml/2006/7/11/474).
Related history:
- https://lkml.org/lkml/2006/12/27/123 is an example of someone
realizing that fexecve() is likely to fail in a chroot environment.
- http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043 covered
documenting the /proc requirement of fexecve(3) in its manpage, to
"prevent other people from wasting their time".
- https://bugzilla.redhat.com/show_bug.cgi?id=241609 described a
problem where a process that did setuid() could not fexecve()
because it no longer had access to /proc/self/fd; this has since
been fixed.
This patch (of 4):
Add a new execveat(2) system call. execveat() is to execve() as openat()
is to open(): it takes a file descriptor that refers to a directory, and
resolves the filename relative to that.
In addition, if the filename is empty and AT_EMPTY_PATH is specified,
execveat() executes the file to which the file descriptor refers. This
replicates the functionality of fexecve(), which is a system call in other
UNIXen, but in Linux glibc it depends on opening "/proc/self/fd/<fd>" (and
so relies on /proc being mounted).
The filename fed to the executed program as argv[0] (or the name of the
script fed to a script interpreter) will be of the form "/dev/fd/<fd>"
(for an empty filename) or "/dev/fd/<fd>/<filename>", effectively
reflecting how the executable was found. This does however mean that
execution of a script in a /proc-less environment won't work; also, script
execution via an O_CLOEXEC file descriptor fails (as the file will not be
accessible after exec).
Based on patches by Meredydd Luff.
Signed-off-by: David Drysdale <drysdale@google.com>
Cc: Meredydd Luff <meredydd@senatehouse.org>
Cc: Shuah Khan <shuah.kh@samsung.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rich Felker <dalias@aerifal.cx>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-13 03:57:29 +03:00
return do_execveat_common ( AT_FDCWD , filename , argv , envp , 0 ) ;
}
int do_execveat ( int fd , struct filename * filename ,
const char __user * const __user * __argv ,
const char __user * const __user * __envp ,
int flags )
{
struct user_arg_ptr argv = { . ptr . native = __argv } ;
struct user_arg_ptr envp = { . ptr . native = __envp } ;
return do_execveat_common ( fd , filename , argv , envp , flags ) ;
2011-03-06 20:02:54 +03:00
}
# ifdef CONFIG_COMPAT
2014-02-06 00:54:53 +04:00
static int compat_do_execve ( struct filename * filename ,
2012-09-30 21:38:55 +04:00
const compat_uptr_t __user * __argv ,
2012-10-21 05:46:25 +04:00
const compat_uptr_t __user * __envp )
2011-03-06 20:02:54 +03:00
{
struct user_arg_ptr argv = {
. is_compat = true ,
. ptr . compat = __argv ,
} ;
struct user_arg_ptr envp = {
. is_compat = true ,
. ptr . compat = __envp ,
} ;
syscalls: implement execveat() system call
This patchset adds execveat(2) for x86, and is derived from Meredydd
Luff's patch from Sept 2012 (https://lkml.org/lkml/2012/9/11/528).
The primary aim of adding an execveat syscall is to allow an
implementation of fexecve(3) that does not rely on the /proc filesystem,
at least for executables (rather than scripts). The current glibc version
of fexecve(3) is implemented via /proc, which causes problems in sandboxed
or otherwise restricted environments.
Given the desire for a /proc-free fexecve() implementation, HPA suggested
(https://lkml.org/lkml/2006/7/11/556) that an execveat(2) syscall would be
an appropriate generalization.
Also, having a new syscall means that it can take a flags argument without
back-compatibility concerns. The current implementation just defines the
AT_EMPTY_PATH and AT_SYMLINK_NOFOLLOW flags, but other flags could be
added in future -- for example, flags for new namespaces (as suggested at
https://lkml.org/lkml/2006/7/11/474).
Related history:
- https://lkml.org/lkml/2006/12/27/123 is an example of someone
realizing that fexecve() is likely to fail in a chroot environment.
- http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043 covered
documenting the /proc requirement of fexecve(3) in its manpage, to
"prevent other people from wasting their time".
- https://bugzilla.redhat.com/show_bug.cgi?id=241609 described a
problem where a process that did setuid() could not fexecve()
because it no longer had access to /proc/self/fd; this has since
been fixed.
This patch (of 4):
Add a new execveat(2) system call. execveat() is to execve() as openat()
is to open(): it takes a file descriptor that refers to a directory, and
resolves the filename relative to that.
In addition, if the filename is empty and AT_EMPTY_PATH is specified,
execveat() executes the file to which the file descriptor refers. This
replicates the functionality of fexecve(), which is a system call in other
UNIXen, but in Linux glibc it depends on opening "/proc/self/fd/<fd>" (and
so relies on /proc being mounted).
The filename fed to the executed program as argv[0] (or the name of the
script fed to a script interpreter) will be of the form "/dev/fd/<fd>"
(for an empty filename) or "/dev/fd/<fd>/<filename>", effectively
reflecting how the executable was found. This does however mean that
execution of a script in a /proc-less environment won't work; also, script
execution via an O_CLOEXEC file descriptor fails (as the file will not be
accessible after exec).
Based on patches by Meredydd Luff.
Signed-off-by: David Drysdale <drysdale@google.com>
Cc: Meredydd Luff <meredydd@senatehouse.org>
Cc: Shuah Khan <shuah.kh@samsung.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rich Felker <dalias@aerifal.cx>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-13 03:57:29 +03:00
return do_execveat_common ( AT_FDCWD , filename , argv , envp , 0 ) ;
}
static int compat_do_execveat ( int fd , struct filename * filename ,
const compat_uptr_t __user * __argv ,
const compat_uptr_t __user * __envp ,
int flags )
{
struct user_arg_ptr argv = {
. is_compat = true ,
. ptr . compat = __argv ,
} ;
struct user_arg_ptr envp = {
. is_compat = true ,
. ptr . compat = __envp ,
} ;
return do_execveat_common ( fd , filename , argv , envp , flags ) ;
2011-03-06 20:02:37 +03:00
}
2011-03-06 20:02:54 +03:00
# endif
2011-03-06 20:02:37 +03:00
2009-09-24 02:56:59 +04:00
void set_binfmt ( struct linux_binfmt * new )
2005-04-17 02:20:36 +04:00
{
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struct mm_struct * mm = current - > mm ;
if ( mm - > binfmt )
module_put ( mm - > binfmt - > module ) ;
2005-04-17 02:20:36 +04:00
2009-09-24 02:57:41 +04:00
mm - > binfmt = new ;
2009-09-24 02:56:59 +04:00
if ( new )
__module_get ( new - > module ) ;
2005-04-17 02:20:36 +04:00
}
EXPORT_SYMBOL ( set_binfmt ) ;
2007-07-19 12:48:27 +04:00
/*
2014-01-24 03:55:32 +04:00
* set_dumpable stores three - value SUID_DUMP_ * into mm - > flags .
2007-07-19 12:48:27 +04:00
*/
void set_dumpable ( struct mm_struct * mm , int value )
{
2014-01-24 03:55:32 +04:00
if ( WARN_ON ( ( unsigned ) value > SUID_DUMP_ROOT ) )
return ;
2019-03-08 03:29:23 +03:00
set_mask_bits ( & mm - > flags , MMF_DUMPABLE_MASK , value ) ;
2007-07-19 12:48:27 +04:00
}
2012-09-30 21:38:55 +04:00
SYSCALL_DEFINE3 ( execve ,
const char __user * , filename ,
const char __user * const __user * , argv ,
const char __user * const __user * , envp )
{
2014-02-06 00:54:53 +04:00
return do_execve ( getname ( filename ) , argv , envp ) ;
2012-09-30 21:38:55 +04:00
}
syscalls: implement execveat() system call
This patchset adds execveat(2) for x86, and is derived from Meredydd
Luff's patch from Sept 2012 (https://lkml.org/lkml/2012/9/11/528).
The primary aim of adding an execveat syscall is to allow an
implementation of fexecve(3) that does not rely on the /proc filesystem,
at least for executables (rather than scripts). The current glibc version
of fexecve(3) is implemented via /proc, which causes problems in sandboxed
or otherwise restricted environments.
Given the desire for a /proc-free fexecve() implementation, HPA suggested
(https://lkml.org/lkml/2006/7/11/556) that an execveat(2) syscall would be
an appropriate generalization.
Also, having a new syscall means that it can take a flags argument without
back-compatibility concerns. The current implementation just defines the
AT_EMPTY_PATH and AT_SYMLINK_NOFOLLOW flags, but other flags could be
added in future -- for example, flags for new namespaces (as suggested at
https://lkml.org/lkml/2006/7/11/474).
Related history:
- https://lkml.org/lkml/2006/12/27/123 is an example of someone
realizing that fexecve() is likely to fail in a chroot environment.
- http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043 covered
documenting the /proc requirement of fexecve(3) in its manpage, to
"prevent other people from wasting their time".
- https://bugzilla.redhat.com/show_bug.cgi?id=241609 described a
problem where a process that did setuid() could not fexecve()
because it no longer had access to /proc/self/fd; this has since
been fixed.
This patch (of 4):
Add a new execveat(2) system call. execveat() is to execve() as openat()
is to open(): it takes a file descriptor that refers to a directory, and
resolves the filename relative to that.
In addition, if the filename is empty and AT_EMPTY_PATH is specified,
execveat() executes the file to which the file descriptor refers. This
replicates the functionality of fexecve(), which is a system call in other
UNIXen, but in Linux glibc it depends on opening "/proc/self/fd/<fd>" (and
so relies on /proc being mounted).
The filename fed to the executed program as argv[0] (or the name of the
script fed to a script interpreter) will be of the form "/dev/fd/<fd>"
(for an empty filename) or "/dev/fd/<fd>/<filename>", effectively
reflecting how the executable was found. This does however mean that
execution of a script in a /proc-less environment won't work; also, script
execution via an O_CLOEXEC file descriptor fails (as the file will not be
accessible after exec).
Based on patches by Meredydd Luff.
Signed-off-by: David Drysdale <drysdale@google.com>
Cc: Meredydd Luff <meredydd@senatehouse.org>
Cc: Shuah Khan <shuah.kh@samsung.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rich Felker <dalias@aerifal.cx>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-13 03:57:29 +03:00
SYSCALL_DEFINE5 ( execveat ,
int , fd , const char __user * , filename ,
const char __user * const __user * , argv ,
const char __user * const __user * , envp ,
int , flags )
{
int lookup_flags = ( flags & AT_EMPTY_PATH ) ? LOOKUP_EMPTY : 0 ;
return do_execveat ( fd ,
getname_flags ( filename , lookup_flags , NULL ) ,
argv , envp , flags ) ;
}
2012-09-30 21:38:55 +04:00
# ifdef CONFIG_COMPAT
2014-03-04 13:53:50 +04:00
COMPAT_SYSCALL_DEFINE3 ( execve , const char __user * , filename ,
const compat_uptr_t __user * , argv ,
const compat_uptr_t __user * , envp )
2012-09-30 21:38:55 +04:00
{
2014-02-06 00:54:53 +04:00
return compat_do_execve ( getname ( filename ) , argv , envp ) ;
2012-09-30 21:38:55 +04:00
}
syscalls: implement execveat() system call
This patchset adds execveat(2) for x86, and is derived from Meredydd
Luff's patch from Sept 2012 (https://lkml.org/lkml/2012/9/11/528).
The primary aim of adding an execveat syscall is to allow an
implementation of fexecve(3) that does not rely on the /proc filesystem,
at least for executables (rather than scripts). The current glibc version
of fexecve(3) is implemented via /proc, which causes problems in sandboxed
or otherwise restricted environments.
Given the desire for a /proc-free fexecve() implementation, HPA suggested
(https://lkml.org/lkml/2006/7/11/556) that an execveat(2) syscall would be
an appropriate generalization.
Also, having a new syscall means that it can take a flags argument without
back-compatibility concerns. The current implementation just defines the
AT_EMPTY_PATH and AT_SYMLINK_NOFOLLOW flags, but other flags could be
added in future -- for example, flags for new namespaces (as suggested at
https://lkml.org/lkml/2006/7/11/474).
Related history:
- https://lkml.org/lkml/2006/12/27/123 is an example of someone
realizing that fexecve() is likely to fail in a chroot environment.
- http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043 covered
documenting the /proc requirement of fexecve(3) in its manpage, to
"prevent other people from wasting their time".
- https://bugzilla.redhat.com/show_bug.cgi?id=241609 described a
problem where a process that did setuid() could not fexecve()
because it no longer had access to /proc/self/fd; this has since
been fixed.
This patch (of 4):
Add a new execveat(2) system call. execveat() is to execve() as openat()
is to open(): it takes a file descriptor that refers to a directory, and
resolves the filename relative to that.
In addition, if the filename is empty and AT_EMPTY_PATH is specified,
execveat() executes the file to which the file descriptor refers. This
replicates the functionality of fexecve(), which is a system call in other
UNIXen, but in Linux glibc it depends on opening "/proc/self/fd/<fd>" (and
so relies on /proc being mounted).
The filename fed to the executed program as argv[0] (or the name of the
script fed to a script interpreter) will be of the form "/dev/fd/<fd>"
(for an empty filename) or "/dev/fd/<fd>/<filename>", effectively
reflecting how the executable was found. This does however mean that
execution of a script in a /proc-less environment won't work; also, script
execution via an O_CLOEXEC file descriptor fails (as the file will not be
accessible after exec).
Based on patches by Meredydd Luff.
Signed-off-by: David Drysdale <drysdale@google.com>
Cc: Meredydd Luff <meredydd@senatehouse.org>
Cc: Shuah Khan <shuah.kh@samsung.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rich Felker <dalias@aerifal.cx>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-12-13 03:57:29 +03:00
COMPAT_SYSCALL_DEFINE5 ( execveat , int , fd ,
const char __user * , filename ,
const compat_uptr_t __user * , argv ,
const compat_uptr_t __user * , envp ,
int , flags )
{
int lookup_flags = ( flags & AT_EMPTY_PATH ) ? LOOKUP_EMPTY : 0 ;
return compat_do_execveat ( fd ,
getname_flags ( filename , lookup_flags , NULL ) ,
argv , envp , flags ) ;
}
2012-09-30 21:38:55 +04:00
# endif