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Since the parse_args() stops parsing at '--', bootconfig_params()
will never get the '--' as param and initargs_found never be true.
In the result, if we pass some init arguments via the bootconfig,
those are always appended to the kernel command line with '--'
even if the kernel command line already has '--'.
To fix this correctly, check the return value of parse_args()
and set initargs_found true if the return value is not an error
but a valid address.
Link: https://lkml.kernel.org/r/159650953285.270383.14822353843556363851.stgit@devnote2
Fixes: f61872bb58a1 ("bootconfig: Use parse_args() to find bootconfig and '--'")
Cc: stable@vger.kernel.org
Reported-by: Arvind Sankar <nivedita@alum.mit.edu>
Suggested-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
- Introduce CONFIG_INIT_STACK_ALL_ZERO (Alexander Potapenko)
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Merge tag 'var-init-v5.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux
Pull automatic variable initialization updates from Kees Cook:
"This adds the "zero" init option from Clang, which is being used
widely in production builds of Android and Chrome OS (though it also
keeps the "pattern" init, which is better for debug builds).
- Introduce CONFIG_INIT_STACK_ALL_ZERO (Alexander Potapenko)"
* tag 'var-init-v5.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
security: allow using Clang's zero initialization for stack variables
When booting on 32-bit machines (seen on OpenRISC) I saw this warning
with CONFIG_DEBUG_MUTEXES turned on.
------------[ cut here ]------------
WARNING: CPU: 0 PID: 0 at kernel/locking/mutex.c:1242 __mutex_unlock_slowpath+0x328/0x3ec
DEBUG_LOCKS_WARN_ON(__owner_task(owner) != current)
Modules linked in:
CPU: 0 PID: 0 Comm: swapper Not tainted 5.8.0-rc1-simple-smp-00005-g2864e2171db4-dirty #179
Call trace:
[<(ptrval)>] dump_stack+0x34/0x48
[<(ptrval)>] __warn+0x104/0x158
[<(ptrval)>] ? __mutex_unlock_slowpath+0x328/0x3ec
[<(ptrval)>] warn_slowpath_fmt+0x7c/0x94
[<(ptrval)>] __mutex_unlock_slowpath+0x328/0x3ec
[<(ptrval)>] mutex_unlock+0x18/0x28
[<(ptrval)>] __cpuhp_setup_state_cpuslocked.part.0+0x29c/0x2f4
[<(ptrval)>] ? page_alloc_cpu_dead+0x0/0x30
[<(ptrval)>] ? start_kernel+0x0/0x684
[<(ptrval)>] __cpuhp_setup_state+0x4c/0x5c
[<(ptrval)>] page_alloc_init+0x34/0x68
[<(ptrval)>] ? start_kernel+0x1a0/0x684
[<(ptrval)>] ? early_init_dt_scan_nodes+0x60/0x70
irq event stamp: 0
I traced this to kernel/locking/mutex.c storing 3 bits of MUTEX_FLAGS in
the task_struct pointer (mutex.owner). There is a comment saying that
task_structs are always aligned to L1_CACHE_BYTES. This is not true for
the init_task.
On 64-bit machines this is not a problem because symbol addresses are
naturally aligned to 64-bits providing 3 bits for MUTEX_FLAGS. Howerver,
for 32-bit machines the symbol address only has 2 bits available.
Fix this by setting init_task alignment to at least L1_CACHE_BYTES.
Signed-off-by: Stafford Horne <shorne@gmail.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'x86-cleanups-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 cleanups from Ingo Molnar:
"Misc cleanups all around the place"
* tag 'x86-cleanups-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/ioperm: Initialize pointer bitmap with NULL rather than 0
x86: uv: uv_hub.h: Delete duplicated word
x86: cmpxchg_32.h: Delete duplicated word
x86: bootparam.h: Delete duplicated word
x86/mm: Remove the unused mk_kernel_pgd() #define
x86/tsc: Remove unused "US_SCALE" and "NS_SCALE" leftover macros
x86/ioapic: Remove unused "IOAPIC_AUTO" define
x86/mm: Drop unused MAX_PHYSADDR_BITS
x86/msr: Move the F15h MSRs where they belong
x86/idt: Make idt_descr static
initrd: Remove erroneous comment
x86/mm/32: Fix -Wmissing prototypes warnings for init.c
cpu/speculation: Add prototype for cpu_show_srbds()
x86/mm: Fix -Wmissing-prototypes warnings for arch/x86/mm/init.c
x86/asm: Unify __ASSEMBLY__ blocks
x86/cpufeatures: Mark two free bits in word 3
x86/msr: Lift AMD family 0x15 power-specific MSRs
kernel and initrd images.
ZSTD has a very fast decompressor, yet it compresses better than gzip.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'x86-boot-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 boot updates from Ingo Molnar:
"The main change in this cycle was to add support for ZSTD-compressed
kernel and initrd images.
ZSTD has a very fast decompressor, yet it compresses better than gzip"
* tag 'x86-boot-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
Documentation: dontdiff: Add zstd compressed files
.gitignore: Add ZSTD-compressed files
x86: Add support for ZSTD compressed kernel
x86: Bump ZO_z_extra_bytes margin for zstd
usr: Add support for zstd compressed initramfs
init: Add support for zstd compressed kernel
lib: Add zstd support to decompress
lib: Prepare zstd for preboot environment, improve performance
- Add the zstd and zstd22 cmds to scripts/Makefile.lib
- Add the HAVE_KERNEL_ZSTD and KERNEL_ZSTD options
Architecture specific support is still needed for decompression.
Signed-off-by: Nick Terrell <terrelln@fb.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20200730190841.2071656-4-nickrterrell@gmail.com
Add a simple helper to set timestamps with a kernel space file name and
switch the early init code over to it.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Add a simple helper to mknod with a kernel space file name and switch
the early init code over to it. Remove the now unused ksys_mknod.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Add a simple helper to mkdir with a kernel space file name and switch
the early init code over to it. Remove the now unused ksys_mkdir.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Add a simple helper to symlink with a kernel space file name and switch
the early init code over to it. Remove the now unused ksys_symlink.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Add a simple helper to link with a kernel space file name and switch
the early init code over to it. Remove the now unused ksys_link.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Add a simple helper to check if a file exists based on kernel space file
name and switch the early init code over to it. Note that this
theoretically changes behavior as it always is based on the effective
permissions. But during early init that doesn't make a difference.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Add a simple helper to chroot with a kernel space file name and switch
the early init code over to it. Remove the now unused ksys_chroot.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Add a simple helper to chdir with a kernel space file name and switch
the early init code over to it. Remove the now unused ksys_chdir.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Add a simple helper to rmdir with a kernel space file name and switch
the early init code over to it. Remove the now unused ksys_rmdir.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Add a simple helper to unlink with a kernel space file name and switch
the early init code over to it. Remove the now unused ksys_unlink.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Like ksys_umount, but takes a kernel pointer for the destination path.
Switch over the umount in the init code, which just happen to work due to
the implicit set_fs(KERNEL_DS) during early init right now.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Like do_mount, but takes a kernel pointer for the destination path.
Switch over the mounts in the init code and devtmpfs to it, which
just happen to work due to the implicit set_fs(KERNEL_DS) during early
init right now.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Set ramdisk_execute_command to "/init" at compile time. The command
line can still override it, but this saves a few instructions and
removes a NULL check.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Don't bother saving away the pathname and just use the new struct path
based utimes helper instead.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Don't rely on the implicit set_fs(KERNEL_DS) for ksys_open to work, but
instead open a struct file for /dev/console and then install it as FD
0/1/2 manually.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
There is no good reason to mess with file descriptors from in-kernel
code, switch the initramfs unpacking to struct file based write
instead.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
There is no point in trying to clean up after unpacking the initramfs
failed, as it should never get past the magic number check. In addition
the current code only removes file that are direct children of the root
entry, which wasn't complete anyway
Fixes: df52092f3c97 ("fastboot: remove duplicate unpack_to_rootfs()")
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
If initrd support is not enable just print the warning directly instead
of hiding the fact that we just failed behind two stub functions.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
The classic initial ramdisk has been replaced by the much more
flexible and efficient initramfs a long time. Warn about it being
removed soon.
Includes a spelling fix from Colin Ian King <colin.king@canonical.com>.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
There is no good reason to mess with file descriptors from in-kernel
code, switch the initrd loading to struct file based read and writes
instead.
Also Pass an explicit offset instead of ->f_pos, and to make that easier,
use file scope file structs and offsets everywhere except for
identify_ramdisk_image instead of the current strange mix.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
BLKFLSBUF used to be overloaded for the ramdisk driver to free the whole
ramdisk, which was completely different behavior compared to all other
drivers. But this magic overload got removed in commit ff26956875c2
("brd: remove support for BLKFLSBUF"), so this call is entirely
pointless now.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Remove the special handling for multiple floppies in the initrd code.
No one should be using floppies for booting these days. (famous last
words..)
Includes a spelling fix from Colin Ian King <colin.king@canonical.com>.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
A sequence counter write side critical section must be protected by some
form of locking to serialize writers. A plain seqcount_t does not
contain the information of which lock must be held when entering a write
side critical section.
Use the new seqcount_spinlock_t data type, which allows to associate a
spinlock with the sequence counter. This enables lockdep to verify that
the spinlock used for writer serialization is held when the write side
critical section is entered.
If lockdep is disabled this lock association is compiled out and has
neither storage size nor runtime overhead.
Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200720155530.1173732-14-a.darwish@linutronix.de
Qian reported that the current setup forgoes the Kconfig dependencies and
results in warnings such as:
WARNING: unmet direct dependencies detected for SCHED_THERMAL_PRESSURE
Depends on [n]: SMP [=y] && CPU_FREQ_THERMAL [=n]
Selected by [y]:
- ARM64 [=y]
Revert commit
e17ae7fea871 ("arm, arm64: Select CONFIG_SCHED_THERMAL_PRESSURE")
and re-implement it by making the option default to 'y' for arm64 and arm,
which respects Kconfig dependencies (i.e. will remain 'n' if
CPU_FREQ_THERMAL=n).
Fixes: e17ae7fea871 ("arm, arm64: Select CONFIG_SCHED_THERMAL_PRESSURE")
Reported-by: Qian Cai <cai@lca.pw>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200729135718.1871-1-valentin.schneider@arm.com
As Russell pointed out [1], this option is severely lacking in the
documentation department, and figuring out if one has the required
dependencies to benefit from turning it on is not straightforward.
Make it non user-visible, and add a bit of help to it. While at it, make it
depend on CPU_FREQ_THERMAL.
[1]: https://lkml.kernel.org/r/20200603173150.GB1551@shell.armlinux.org.uk
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200712165917.9168-3-valentin.schneider@arm.com
To allow the kernel not to play games with set_fs to call exec
implement kernel_execve. The function kernel_execve takes pointers
into kernel memory and copies the values pointed to onto the new
userspace stack.
The calls with arguments from kernel space of do_execve are replaced
with calls to kernel_execve.
The calls do_execve and do_execveat are made static as there are now
no callers outside of exec.
The comments that mention do_execve are updated to refer to
kernel_execve or execve depending on the circumstances. In addition
to correcting the comments, this makes it easy to grep for do_execve
and verify it is not used.
Inspired-by: https://lkml.kernel.org/r/20200627072704.2447163-1-hch@lst.de
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/87wo365ikj.fsf@x220.int.ebiederm.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Just like the NFS and CIFS root code this better lives with the
driver it is tightly integrated with.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Song Liu <song@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
The only caller of the bstat function becomes cleaner and simpler when
open coding the function.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: NeilBrown <neilb@suse.de>
Acked-by: Song Liu <song@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
A common question asked when debugging seccomp filters is "how many
filters are attached to your process?" Provide a way to easily answer
this question through /proc/$pid/status with a "Seccomp_filters" line.
Signed-off-by: Kees Cook <keescook@chromium.org>
scripts/cc-can-link.sh tests if the compiler can link userspace
programs.
When $(CC) is GCC, it is checked against the target architecture
because the toolchain prefix is specified as a part of $(CC).
When $(CC) is Clang, it is checked against the host architecture
because --target option is missing.
Pass $(CLANG_FLAGS) to scripts/cc-can-link.sh to evaluate the link
capability for the target architecture.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
The nommu-mmap.txt file provides description of user visible
behaviuour. So, move it to the admin-guide.
As it is already at the ReST, also rename it.
Suggested-by: Mike Rapoport <rppt@linux.ibm.com>
Suggested-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/3a63d1833b513700755c85bf3bda0a6c4ab56986.1592918949.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Most architectures have been passing the location of an initrd via the
initrd= option since their inception. Remove the comment as it's both
wrong and unrelated to the commit that introduced it.
For a bit more context, I assume there's been some confusion between
"initrd" being a keyword in things like extlinux.conf and also that for
quite a long time now initrd information is passed via device tree and
not the command line on relevant architectures. But it's still true that
it's been a valid command line option to the kernel since the 90s. It's
just the case that in 2018 the code was consolidated from under arch/
and in to this file.
[ bp: Move the context clarification up into the commit message proper. ]
Fixes: 694cfd87b0c8 ("x86/setup: Add an initrdmem= option to specify initrd physical address")
Signed-off-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200619143056.24538-1-trini@konsulko.com
In addition to -ftrivial-auto-var-init=pattern (used by
CONFIG_INIT_STACK_ALL now) Clang also supports zero initialization for
locals enabled by -ftrivial-auto-var-init=zero. The future of this flag
is still being debated (see https://bugs.llvm.org/show_bug.cgi?id=45497).
Right now it is guarded by another flag,
-enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang,
which means it may not be supported by future Clang releases. Another
possible resolution is that -ftrivial-auto-var-init=zero will persist
(as certain users have already started depending on it), but the name
of the guard flag will change.
In the meantime, zero initialization has proven itself as a good
production mitigation measure against uninitialized locals. Unlike pattern
initialization, which has a higher chance of triggering existing bugs,
zero initialization provides safe defaults for strings, pointers, indexes,
and sizes. On the other hand, pattern initialization remains safer for
return values. Chrome OS and Android are moving to using zero
initialization for production builds.
Performance-wise, the difference between pattern and zero initialization
is usually negligible, although the generated code for zero
initialization is more compact.
This patch renames CONFIG_INIT_STACK_ALL to CONFIG_INIT_STACK_ALL_PATTERN
and introduces another config option, CONFIG_INIT_STACK_ALL_ZERO, that
enables zero initialization for locals if the corresponding flags are
supported by Clang.
Cc: Kees Cook <keescook@chromium.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Alexander Potapenko <glider@google.com>
Link: https://lore.kernel.org/r/20200616083435.223038-1-glider@google.com
Reviewed-by: Maciej Żenczykowski <maze@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
- fix build rules in binderfs sample
- fix build errors when Kbuild recurses to the top Makefile
- covert '---help---' in Kconfig to 'help'
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Merge tag 'kbuild-v5.8-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild
Pull more Kbuild updates from Masahiro Yamada:
- fix build rules in binderfs sample
- fix build errors when Kbuild recurses to the top Makefile
- covert '---help---' in Kconfig to 'help'
* tag 'kbuild-v5.8-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
treewide: replace '---help---' in Kconfig files with 'help'
kbuild: fix broken builds because of GZIP,BZIP2,LZOP variables
samples: binderfs: really compile this sample and fix build issues
Since commit 84af7a6194e4 ("checkpatch: kconfig: prefer 'help' over
'---help---'"), the number of '---help---' has been gradually
decreasing, but there are still more than 2400 instances.
This commit finishes the conversion. While I touched the lines,
I also fixed the indentation.
There are a variety of indentation styles found.
a) 4 spaces + '---help---'
b) 7 spaces + '---help---'
c) 8 spaces + '---help---'
d) 1 space + 1 tab + '---help---'
e) 1 tab + '---help---' (correct indentation)
f) 1 tab + 1 space + '---help---'
g) 1 tab + 2 spaces + '---help---'
In order to convert all of them to 1 tab + 'help', I ran the
following commend:
$ find . -name 'Kconfig*' | xargs sed -i 's/^[[:space:]]*---help---/\thelp/'
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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Merge tag 'notifications-20200601' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs
Pull notification queue from David Howells:
"This adds a general notification queue concept and adds an event
source for keys/keyrings, such as linking and unlinking keys and
changing their attributes.
Thanks to Debarshi Ray, we do have a pull request to use this to fix a
problem with gnome-online-accounts - as mentioned last time:
https://gitlab.gnome.org/GNOME/gnome-online-accounts/merge_requests/47
Without this, g-o-a has to constantly poll a keyring-based kerberos
cache to find out if kinit has changed anything.
[ There are other notification pending: mount/sb fsinfo notifications
for libmount that Karel Zak and Ian Kent have been working on, and
Christian Brauner would like to use them in lxc, but let's see how
this one works first ]
LSM hooks are included:
- A set of hooks are provided that allow an LSM to rule on whether or
not a watch may be set. Each of these hooks takes a different
"watched object" parameter, so they're not really shareable. The
LSM should use current's credentials. [Wanted by SELinux & Smack]
- A hook is provided to allow an LSM to rule on whether or not a
particular message may be posted to a particular queue. This is
given the credentials from the event generator (which may be the
system) and the watch setter. [Wanted by Smack]
I've provided SELinux and Smack with implementations of some of these
hooks.
WHY
===
Key/keyring notifications are desirable because if you have your
kerberos tickets in a file/directory, your Gnome desktop will monitor
that using something like fanotify and tell you if your credentials
cache changes.
However, we also have the ability to cache your kerberos tickets in
the session, user or persistent keyring so that it isn't left around
on disk across a reboot or logout. Keyrings, however, cannot currently
be monitored asynchronously, so the desktop has to poll for it - not
so good on a laptop. This facility will allow the desktop to avoid the
need to poll.
DESIGN DECISIONS
================
- The notification queue is built on top of a standard pipe. Messages
are effectively spliced in. The pipe is opened with a special flag:
pipe2(fds, O_NOTIFICATION_PIPE);
The special flag has the same value as O_EXCL (which doesn't seem
like it will ever be applicable in this context)[?]. It is given up
front to make it a lot easier to prohibit splice&co from accessing
the pipe.
[?] Should this be done some other way? I'd rather not use up a new
O_* flag if I can avoid it - should I add a pipe3() system call
instead?
The pipe is then configured::
ioctl(fds[1], IOC_WATCH_QUEUE_SET_SIZE, queue_depth);
ioctl(fds[1], IOC_WATCH_QUEUE_SET_FILTER, &filter);
Messages are then read out of the pipe using read().
- It should be possible to allow write() to insert data into the
notification pipes too, but this is currently disabled as the
kernel has to be able to insert messages into the pipe *without*
holding pipe->mutex and the code to make this work needs careful
auditing.
- sendfile(), splice() and vmsplice() are disabled on notification
pipes because of the pipe->mutex issue and also because they
sometimes want to revert what they just did - but one or more
notification messages might've been interleaved in the ring.
- The kernel inserts messages with the wait queue spinlock held. This
means that pipe_read() and pipe_write() have to take the spinlock
to update the queue pointers.
- Records in the buffer are binary, typed and have a length so that
they can be of varying size.
This allows multiple heterogeneous sources to share a common
buffer; there are 16 million types available, of which I've used
just a few, so there is scope for others to be used. Tags may be
specified when a watchpoint is created to help distinguish the
sources.
- Records are filterable as types have up to 256 subtypes that can be
individually filtered. Other filtration is also available.
- Notification pipes don't interfere with each other; each may be
bound to a different set of watches. Any particular notification
will be copied to all the queues that are currently watching for it
- and only those that are watching for it.
- When recording a notification, the kernel will not sleep, but will
rather mark a queue as having lost a message if there's
insufficient space. read() will fabricate a loss notification
message at an appropriate point later.
- The notification pipe is created and then watchpoints are attached
to it, using one of:
keyctl_watch_key(KEY_SPEC_SESSION_KEYRING, fds[1], 0x01);
watch_mount(AT_FDCWD, "/", 0, fd, 0x02);
watch_sb(AT_FDCWD, "/mnt", 0, fd, 0x03);
where in both cases, fd indicates the queue and the number after is
a tag between 0 and 255.
- Watches are removed if either the notification pipe is destroyed or
the watched object is destroyed. In the latter case, a message will
be generated indicating the enforced watch removal.
Things I want to avoid:
- Introducing features that make the core VFS dependent on the
network stack or networking namespaces (ie. usage of netlink).
- Dumping all this stuff into dmesg and having a daemon that sits
there parsing the output and distributing it as this then puts the
responsibility for security into userspace and makes handling
namespaces tricky. Further, dmesg might not exist or might be
inaccessible inside a container.
- Letting users see events they shouldn't be able to see.
TESTING AND MANPAGES
====================
- The keyutils tree has a pipe-watch branch that has keyctl commands
for making use of notifications. Proposed manual pages can also be
found on this branch, though a couple of them really need to go to
the main manpages repository instead.
If the kernel supports the watching of keys, then running "make
test" on that branch will cause the testing infrastructure to spawn
a monitoring process on the side that monitors a notifications pipe
for all the key/keyring changes induced by the tests and they'll
all be checked off to make sure they happened.
https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/keyutils.git/log/?h=pipe-watch
- A test program is provided (samples/watch_queue/watch_test) that
can be used to monitor for keyrings, mount and superblock events.
Information on the notifications is simply logged to stdout"
* tag 'notifications-20200601' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
smack: Implement the watch_key and post_notification hooks
selinux: Implement the watch_key security hook
keys: Make the KEY_NEED_* perms an enum rather than a mask
pipe: Add notification lossage handling
pipe: Allow buffers to be marked read-whole-or-error for notifications
Add sample notification program
watch_queue: Add a key/keyring notification facility
security: Add hooks to rule on setting a watch
pipe: Add general notification queue support
pipe: Add O_NOTIFICATION_PIPE
security: Add a hook for the point of notification insertion
uapi: General notification queue definitions
Merge the state of the locking kcsan branch before the read/write_once()
and the atomics modifications got merged.
Squash the fallout of the rebase on top of the read/write once and atomic
fallback work into the merge. The history of the original branch is
preserved in tag locking-kcsan-2020-06-02.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
