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No need to lock parent just because of ->d_revalidate() on child;
contrary to the stale comment, lookup_dcache() *can* be used without
locking the parent. Result can be moved as soon as we return, of
course, but the same is true for lookup_one_len_unlocked() itself.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Have lookup_fast() return 1 on success and 0 on "need to fall back";
lookup_slow() and follow_managed() return positive (1) on success.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
... otherwise d_is_symlink() above might have nothing to do with
the inode value we've got.
Cc: stable@vger.kernel.org # v4.2+
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
both do_last() and walk_component() risk picking a NULL inode out
of dentry about to become positive, *then* checking its flags and
seeing that it's not negative anymore and using (already stale by
then) value they'd fetched earlier. Usually ends up oopsing soon
after that...
Cc: stable@vger.kernel.org # v3.13+
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
... into returning a positive to path_openat(), which would interpret that
as "symlink had been encountered" and proceed to corrupt memory, etc.
It can only happen due to a bug in some ->open() instance or in some LSM
hook, etc., so we report any such event *and* make sure it doesn't trick
us into further unpleasantness.
Cc: stable@vger.kernel.org # v3.6+, at least
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
parallel to mutex_{lock,unlock,trylock,is_locked,lock_nested},
inode_foo(inode) being mutex_foo(&inode->i_mutex).
Please, use those for access to ->i_mutex; over the coming cycle
->i_mutex will become rwsem, with ->lookup() done with it held
only shared.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull misc vfs updates from Al Viro:
"All kinds of stuff. That probably should've been 5 or 6 separate
branches, but by the time I'd realized how large and mixed that bag
had become it had been too close to -final to play with rebasing.
Some fs/namei.c cleanups there, memdup_user_nul() introduction and
switching open-coded instances, burying long-dead code, whack-a-mole
of various kinds, several new helpers for ->llseek(), assorted
cleanups and fixes from various people, etc.
One piece probably deserves special mention - Neil's
lookup_one_len_unlocked(). Similar to lookup_one_len(), but gets
called without ->i_mutex and tries to avoid ever taking it. That, of
course, means that it's not useful for any directory modifications,
but things like getting inode attributes in nfds readdirplus are fine
with that. I really should've asked for moratorium on lookup-related
changes this cycle, but since I hadn't done that early enough... I
*am* asking for that for the coming cycle, though - I'm going to try
and get conversion of i_mutex to rwsem with ->lookup() done under lock
taken shared.
There will be a patch closer to the end of the window, along the lines
of the one Linus had posted last May - mechanical conversion of
->i_mutex accesses to inode_lock()/inode_unlock()/inode_trylock()/
inode_is_locked()/inode_lock_nested(). To quote Linus back then:
-----
| This is an automated patch using
|
| sed 's/mutex_lock(&\(.*\)->i_mutex)/inode_lock(\1)/'
| sed 's/mutex_unlock(&\(.*\)->i_mutex)/inode_unlock(\1)/'
| sed 's/mutex_lock_nested(&\(.*\)->i_mutex,[ ]*I_MUTEX_\([A-Z0-9_]*\))/inode_lock_nested(\1, I_MUTEX_\2)/'
| sed 's/mutex_is_locked(&\(.*\)->i_mutex)/inode_is_locked(\1)/'
| sed 's/mutex_trylock(&\(.*\)->i_mutex)/inode_trylock(\1)/'
|
| with a very few manual fixups
-----
I'm going to send that once the ->i_mutex-affecting stuff in -next
gets mostly merged (or when Linus says he's about to stop taking
merges)"
* 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (63 commits)
nfsd: don't hold i_mutex over userspace upcalls
fs:affs:Replace time_t with time64_t
fs/9p: use fscache mutex rather than spinlock
proc: add a reschedule point in proc_readfd_common()
logfs: constify logfs_block_ops structures
fcntl: allow to set O_DIRECT flag on pipe
fs: __generic_file_splice_read retry lookup on AOP_TRUNCATED_PAGE
fs: xattr: Use kvfree()
[s390] page_to_phys() always returns a multiple of PAGE_SIZE
nbd: use ->compat_ioctl()
fs: use block_device name vsprintf helper
lib/vsprintf: add %*pg format specifier
fs: use gendisk->disk_name where possible
poll: plug an unused argument to do_poll
amdkfd: don't open-code memdup_user()
cdrom: don't open-code memdup_user()
rsxx: don't open-code memdup_user()
mtip32xx: don't open-code memdup_user()
[um] mconsole: don't open-code memdup_user_nul()
[um] hostaudio: don't open-code memdup_user()
...
We need information about exports when crossing mountpoints during
lookup or NFSv4 readdir. If we don't already have that information
cached, we may have to ask (and wait for) rpc.mountd.
In both cases we currently hold the i_mutex on the parent of the
directory we're asking rpc.mountd about. We've seen situations where
rpc.mountd performs some operation on that directory that tries to take
the i_mutex again, resulting in deadlock.
With some care, we may be able to avoid that in rpc.mountd. But it
seems better just to avoid holding a mutex while waiting on userspace.
It appears that lookup_one_len is pretty much the only operation that
needs the i_mutex. So we could just drop the i_mutex elsewhere and do
something like
mutex_lock()
lookup_one_len()
mutex_unlock()
In many cases though the lookup would have been cached and not required
the i_mutex, so it's more efficient to create a lookup_one_len() variant
that only takes the i_mutex when necessary.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
new method: ->get_link(); replacement of ->follow_link(). The differences
are:
* inode and dentry are passed separately
* might be called both in RCU and non-RCU mode;
the former is indicated by passing it a NULL dentry.
* when called that way it isn't allowed to block
and should return ERR_PTR(-ECHILD) if it needs to be called
in non-RCU mode.
It's a flagday change - the old method is gone, all in-tree instances
converted. Conversion isn't hard; said that, so far very few instances
do not immediately bail out when called in RCU mode. That'll change
in the next commits.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
kmap() in page_follow_link_light() needed to go - allowing to hold
an arbitrary number of kmaps for long is a great way to deadlocking
the system.
new helper (inode_nohighmem(inode)) needs to be used for pagecache
symlinks inodes; done for all in-tree cases. page_follow_link_light()
instrumented to yell about anything missed.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
that allows to kill the recheck of nd->seq on the way out in
this case, and this check on the way out is left only for
absolute pathnames.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
we already zero it on outermost set_nameidata(), so initialization in
path_init() is pointless and wrong. The same DoS exists on pre-4.2
kernels, but there a slightly different fix will be needed.
Cc: stable@vger.kernel.org # v4.2
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Merge second patch-bomb from Andrew Morton:
- most of the rest of MM
- procfs
- lib/ updates
- printk updates
- bitops infrastructure tweaks
- checkpatch updates
- nilfs2 update
- signals
- various other misc bits: coredump, seqfile, kexec, pidns, zlib, ipc,
dma-debug, dma-mapping, ...
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (102 commits)
ipc,msg: drop dst nil validation in copy_msg
include/linux/zutil.h: fix usage example of zlib_adler32()
panic: release stale console lock to always get the logbuf printed out
dma-debug: check nents in dma_sync_sg*
dma-mapping: tidy up dma_parms default handling
pidns: fix set/getpriority and ioprio_set/get in PRIO_USER mode
kexec: use file name as the output message prefix
fs, seqfile: always allow oom killer
seq_file: reuse string_escape_str()
fs/seq_file: use seq_* helpers in seq_hex_dump()
coredump: change zap_threads() and zap_process() to use for_each_thread()
coredump: ensure all coredumping tasks have SIGNAL_GROUP_COREDUMP
signal: remove jffs2_garbage_collect_thread()->allow_signal(SIGCONT)
signal: introduce kernel_signal_stop() to fix jffs2_garbage_collect_thread()
signal: turn dequeue_signal_lock() into kernel_dequeue_signal()
signals: kill block_all_signals() and unblock_all_signals()
nilfs2: fix gcc uninitialized-variable warnings in powerpc build
nilfs2: fix gcc unused-but-set-variable warnings
MAINTAINERS: nilfs2: add header file for tracing
nilfs2: add tracepoints for analyzing reading and writing metadata files
...
Pull trivial updates from Jiri Kosina:
"Trivial stuff from trivial tree that can be trivially summed up as:
- treewide drop of spurious unlikely() before IS_ERR() from Viresh
Kumar
- cosmetic fixes (that don't really affect basic functionality of the
driver) for pktcdvd and bcache, from Julia Lawall and Petr Mladek
- various comment / printk fixes and updates all over the place"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial:
bcache: Really show state of work pending bit
hwmon: applesmc: fix comment typos
Kconfig: remove comment about scsi_wait_scan module
class_find_device: fix reference to argument "match"
debugfs: document that debugfs_remove*() accepts NULL and error values
net: Drop unlikely before IS_ERR(_OR_NULL)
mm: Drop unlikely before IS_ERR(_OR_NULL)
fs: Drop unlikely before IS_ERR(_OR_NULL)
drivers: net: Drop unlikely before IS_ERR(_OR_NULL)
drivers: misc: Drop unlikely before IS_ERR(_OR_NULL)
UBI: Update comments to reflect UBI_METAONLY flag
pktcdvd: drop null test before destroy functions
There are many places which use mapping_gfp_mask to restrict a more
generic gfp mask which would be used for allocations which are not
directly related to the page cache but they are performed in the same
context.
Let's introduce a helper function which makes the restriction explicit and
easier to track. This patch doesn't introduce any functional changes.
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Michal Hocko <mhocko@suse.com>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull userns hardlink capability check fix from Eric Biederman:
"This round just contains a single patch. There has been a lot of
other work this period but it is not quite ready yet, so I am pushing
it until 4.5.
The remaining change by Dirk Steinmetz wich fixes both Gentoo and
Ubuntu containers allows hardlinks if we have the appropriate
capabilities in the user namespace. Security wise it is really a
gimme as the user namespace root can already call setuid become that
user and create the hardlink"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
namei: permit linking with CAP_FOWNER in userns
Attempting to hardlink to an unsafe file (e.g. a setuid binary) from
within an unprivileged user namespace fails, even if CAP_FOWNER is held
within the namespace. This may cause various failures, such as a gentoo
installation within a lxc container failing to build and install specific
packages.
This change permits hardlinking of files owned by mapped uids, if
CAP_FOWNER is held for that namespace. Furthermore, it improves consistency
by using the existing inode_owner_or_capable(), which is aware of
namespaced capabilities as of 23adbe12ef ("fs,userns: Change
inode_capable to capable_wrt_inode_uidgid").
Signed-off-by: Dirk Steinmetz <public@rsjtdrjgfuzkfg.com>
This is hitting us in Ubuntu during some dpkg upgrades in containers.
When upgrading a file dpkg creates a hard link to the old file to back
it up before overwriting it. When packages upgrade suid files owned by a
non-root user the link isn't permitted, and the package upgrade fails.
This patch fixes our problem.
Tested-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Leandro Awa writes:
"After switching to version 4.1.6, our parallelized and distributed
workflows now fail consistently with errors of the form:
T34: ./regex.c:39:22: error: config.h: No such file or directory
From our 'git bisect' testing, the following commit appears to be the
possible cause of the behavior we've been seeing: commit 766c4cbfacd8"
Al Viro says:
"What happens is that 766c4cbfac got the things subtly wrong.
We used to treat d_is_negative() after lookup_fast() as "fall with
ENOENT". That was wrong - checking ->d_flags outside of ->d_seq
protection is unreliable and failing with hard error on what should've
fallen back to non-RCU pathname resolution is a bug.
Unfortunately, we'd pulled the test too far up and ran afoul of
another kind of staleness. The dentry might have been absolutely
stable from the RCU point of view (and we might be on UP, etc), but
stale from the remote fs point of view. If ->d_revalidate() returns
"it's actually stale", dentry gets thrown away and the original code
wouldn't even have looked at its ->d_flags.
What we need is to check ->d_flags where 766c4cbfac does (prior to
->d_seq validation) but only use the result in cases where we do not
discard this dentry outright"
Reported-by: Leandro Awa <lawa@nvidia.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=104911
Fixes: 766c4cbfac ("namei: d_is_negative() should be checked...")
Tested-by: Leandro Awa <lawa@nvidia.com>
Cc: stable@vger.kernel.org # v4.1+
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
IS_ERR(_OR_NULL) already contain an 'unlikely' compiler flag and there
is no need to do that again from its callers. Drop it.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Jeff Layton <jlayton@poochiereds.net>
Reviewed-by: David Howells <dhowells@redhat.com>
Reviewed-by: Steve French <smfrench@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Fix the following warnings:
Warning(.//fs/namei.c:2422): No description found for parameter 'nd'
Warning(.//fs/namei.c:2422): Excess function parameter 'nameidata'
description in 'path_mountpoint'
Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In rare cases a directory can be renamed out from under a bind mount.
In those cases without special handling it becomes possible to walk up
the directory tree to the root dentry of the filesystem and down
from the root dentry to every other file or directory on the filesystem.
Like division by zero .. from an unconnected path can not be given
a useful semantic as there is no predicting at which path component
the code will realize it is unconnected. We certainly can not match
the current behavior as the current behavior is a security hole.
Therefore when encounting .. when following an unconnected path
return -ENOENT.
- Add a function path_connected to verify path->dentry is reachable
from path->mnt.mnt_root. AKA to validate that rename did not do
something nasty to the bind mount.
To avoid races path_connected must be called after following a path
component to it's next path component.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Now that we can get there in RCU mode, we shouldn't play with
nd->path.dentry->d_inode - it's not guaranteed to be stable.
Use nd->inode instead.
Reported-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
In RCU mode we might end up with dentry evicted just we check
that it's a directory. In such case we should return ECHILD
rather than ENOTDIR, so that pathwalk would be retries in non-RCU
mode.
Breakage had been introduced in commit b18825a - prior to that
we were looking at nd->inode, which had been fetched before
verifying that ->d_seq was still valid. That form of check
would only be satisfied if at some point the pathname prefix
would indeed have resolved to a non-directory. The fix consists
of checking ->d_seq after we'd run into a non-directory dentry,
and failing with ECHILD in case of mismatch.
Note that all branches since 3.12 have that problem...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
The only caller that cares about its return value can just
as easily pick it from nd->root_seq itself. We used to just
calculate it and return to caller, but these days we are
storing it in nd->root_seq in all cases.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
these guys are always declared next to each other; might as well put
the former (pointer to previous instance) into the latter and simplify
the calling conventions for {set,restore}_nameidata()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
a) make it reject ERR_PTR() for name
b) make it putname(name) on all other failure exits
c) make it return name on success
again, simplifies the callers
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
a) make it reject ERR_PTR() for name
b) make it putname(name) upon return in all other cases.
seriously simplifies the callers...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Otherwise we are risking a hard error where nonlazy restart would be the right
thing to do; it's a very narrow race with mount --move and most of the time it
ends up being completely harmless, but it's possible to construct a case when
we'll get a bogus hard error instead of falling back to non-lazy walk...
For one thing, when crossing _into_ overmount of parent we need to check for
mount_lock bumps when we get NULL from __lookup_mnt() as well.
For another, and less exotically, we need to make sure that the data fetched
in follow_up_rcu() had been consistent. ->mnt_mountpoint is pinned for as
long as it is a mountpoint, but we need to check mount_lock after fetching
to verify that.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
touch_atime is not RCU-safe, and so cannot be called on an RCU walk.
However, in situations where RCU-walk makes a difference, the symlink
will likely to accessed much more often than it is useful to update
the atime.
So split out the test of "Does the atime actually need to be updated"
into atime_needs_update(), and have get_link() unlazy if it finds that
it will need to do that update.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
We are almost done - primitives for leaving RCU mode are aware of nd->stack
now, a new primitive for going to non-RCU mode when we have a symlink on hands
added.
The thing we are heavily relying upon is that *any* unlazy failure will be
shortly followed by terminate_walk(), with no access to nameidata in between.
So it's enough to leave the things in a state terminate_walk() would cope with.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
We *can't* call that audit garbage in RCU mode - it's doing a weird
mix of allocations (GFP_NOFS, immediately followed by GFP_KERNEL)
and I'm not touching that... thing again.
So if this security sclero^Whardening feature gets triggered when
we are in RCU mode, tough - we'll fail with -ECHILD and have
everything restarted in non-RCU mode. Only to hit the same test
and fail, this time with EACCES and with (oh, rapture) an audit spew
produced.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
very simple - just make path_put() conditional on !RCU.
Note that right now it doesn't get called in RCU mode -
we leave it before getting anything into stack.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
inode_follow_link now takes an inode and rcu flag as well as the
dentry.
inode is used in preference to d_backing_inode(dentry), particularly
in RCU-walk mode.
selinux_inode_follow_link() gets dentry_has_perm() and
inode_has_perm() open-coded into it so that it can call
avc_has_perm_flags() in way that is safe if LOOKUP_RCU is set.
Calling avc_has_perm_flags() with rcu_read_lock() held means
that when avc_has_perm_noaudit calls avc_compute_av(), the attempt
to rcu_read_unlock() before calling security_compute_av() will not
actually drop the RCU read-lock.
However as security_compute_av() is completely in a read_lock()ed
region, it should be safe with the RCU read-lock held.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Make use of d_backing_inode() in pathwalk to gain access to an
inode or dentry that's on a lower layer.
Signed-off-by: David Howells <dhowells@redhat.com>
Lift it from link_path_walk(), trailing_symlink(), lookup_last(),
mountpoint_last(), complete_walk() and do_last(). A _lot_ of
those suckers merge.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Make trailing_symlink() return the pathname to traverse or ERR_PTR(-E...).
A subtle point is that for "magic" symlinks it returns "" now - that
leads to link_path_walk("", nd), which is immediately returning 0 and
we are back to the treatment of the last component, at whereever the
damn thing has left us.
Reduces the stack footprint - link_path_walk() called on more shallow
stack now.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* lift link_path_walk() into callers; moving it down into path_init()
had been a mistake. Stack footprint, among other things...
* do _not_ call path_cleanup() after path_init() failure; on all failure
exits out of it we have nothing for path_cleanup() to do
* have path_init() return pathname or ERR_PTR(-E...)
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
we can do fdput() under rcu_read_lock() just fine; all we need to take
care of is fetching nd->inode value first.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Makes the situation much more regular - we avoid a strange state
when the element just after the top of stack is used to store
struct path of symlink, but isn't counted in nd->depth. This
is much more regular, so the normal failure exits, etc., work
fine.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Just store it in nd->stack[nd->depth].link right in pick_link().
Now that we make sure of stack expansion in pick_link(), we can
do so...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
... and don't open-code unlazy_walk() in there - the only reason
for that is to avoid verfication of cached nd->root, which is
trivially avoided by discarding said cached nd->root first.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
rather than letting the callers handle the jump-to-root part of
semantics, do it right in get_link() and return the rest of the
body for the caller to deal with - at that point it's treated
the same way as relative symlinks would be. And return NULL
when there's no "rest of the body" - those are treated the same
as pure jump symlink would be.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Instead of saving name and branching to OK:, where we'll immediately restore
it, and call walk_component() with WALK_PUT|WALK_GET and nd->last_type being
LAST_BIND, which is equivalent to put_link(nd), err = 0, we can just treat
that the same way we'd treat procfs-style "jump" symlinks - do put_link(nd)
and move on.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
when cookie is NULL, put_link() is equivalent to path_put(), so
as soon as we'd set last->cookie to NULL, we can bump nd->depth and
let the normal logics in terminate_walk() to take care of cleanups.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
now that it gets nameidata, no reason to have setting LOOKUP_JUMPED on
mountpoint crossing and calling path_put_conditional() on failures
done in every caller.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
task_struct currently contains two ad-hoc members for use by the VFS:
link_count and total_link_count. These are only interesting to fs/namei.c,
so exposing them explicitly is poor layering. Incidentally, link_count
isn't used anymore, so it can just die.
This patches replaces those with a single pointer to 'struct nameidata'.
This structure represents the current filename lookup of which
there can only be one per process, and is a natural place to
store total_link_count.
This will allow the current "nameidata" argument to all
follow_link operations to be removed as current->nameidata
can be used instead in the _very_ few instances that care about
it at all.
As there are occasional circumstances where pathname lookup can
recurse, such as through kern_path_locked, we always save and old
current->nameidata (if there is one) when setting a new value, and
make sure any active link_counts are preserved.
follow_mount and follow_automount now get a 'struct nameidata *'
rather than 'int flags' so that they can directly access
total_link_count, rather than going through 'current'.
Suggested-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
instead of a single flag (!= 0 => we want to follow symlinks) pass
two bits - WALK_GET (want to follow symlinks) and WALK_PUT (put_link()
once we are done looking at the name). The latter matters only for
success exits - on failure the caller will discard everything anyway.
Suggestions for better variant are welcome; what this thing aims for
is making sure that pending put_link() is done *before* walk_component()
decides to pick a symlink up, rather than between picking it up and
acting upon it. See the next commit for payoff.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
All callers of terminate_walk() are followed by more or less
open-coded eqiuvalent of "do put_link() on everything left
in nd->stack". Better done in terminate_walk() itself, and
when we go for RCU symlink traversal we'll have to do it
there anyway.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
rationale: we'll need to have terminate_walk() do put_link() on
everything, which will mean that in some cases ..._last() will do
put_link() anyway. Easier to have them do it in all cases.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
follow_dotdot_rcu() does an equivalent of terminate_walk() on failure;
shifting it into callers makes for simpler rules and those callers
already have terminate_walk() on other failure exits.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
The only reason why we needed one more was that purely nested
MAXSYMLINKS symlinks could lead to path_init() using that many
entries in addition to nd->stack[0] which it left unused.
That can't happen now - path_init() starts with entry 0 (and
trailing_symlink() is called only when we'd already encountered
one symlink, so no more than MAXSYMLINKS-1 are left).
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
get rid of orig_depth - we only use it on error exit to tell whether
to stop doing put_link() when depth reaches 0 (call from path_init())
or when it reaches 1 (call from trailing_symlink()). However, in
the latter case the caller would immediately follow with one more
put_link(). Just keep doing it until the depth reaches zero (and
simplify trailing_symlink() as the result).
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Get rid of orig_depth checks in OK: logics. If nd->depth is
zero, we had been called from path_init() and we are done.
If it is greater than 1, we are not done, whether we'd been
called from path_init() or trailing_symlink(). And in
case when it's 1, we might have been called from path_init()
and reached the end of nested symlink (in which case
nd->stack[0].name will point to the rest of pathname and
we are not done) or from trailing_symlink(), in which case
we are done.
Just have trailing_symlink() leave NULL in nd->stack[0].name
and use that to discriminate between those cases.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Make link_path_walk() work with any value of nd->depth on entry -
memorize it and use it in tests instead of comparing with 1.
Don't bother with increment/decrement in path_init().
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
move increment of ->depth to the point where we'd discovered
that get_link() has not returned an error, adjust exits
accordingly.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
nd->stack[0] is unused until the handling of trailing symlinks and
we want to get rid of that. Having fucked that transformation up
several times, I went for bloody pedantic series of provably equivalent
transformations. Sorry.
Step 1: keep nd->depth higher by one in link_path_walk() - increment upon
entry, decrement on exits, adjust the arithmetics inside and surround the
calls of functions that care about nd->depth value (nd_alloc_stack(),
get_link(), put_link()) with decrement/increment pairs.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
The only restriction is that on the total amount of symlinks
crossed; how they are nested does not matter
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Array of MAX_NESTED_LINKS + 1 elements put into nameidata;
what used to be a local array in link_path_walk() occupies
entries 1 .. MAX_NESTED_LINKS in it, link and cookie from
the trailing symlink handling loops - entry 0.
This is _not_ the final arrangement; just an easily verified
incremental step.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Deal with skipping leading slashes before what used to be the
recursive call. That way we can get rid of that goto completely.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
absolutely straightforward now - the only variables we need to preserve
across the recursive call are name, link and cookie, and recursion depth
is limited (and can is equal to nd->depth). So arrange an array of
triples to hold instances of those and be done with that.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
reduce the number of returns in there - turn all places
where it returns zero into goto OK and places where it
returns non-zero into goto Err. The only non-trivial
detail is that all breaks in the loop are guaranteed
to be with non-zero err.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
What we do after the second walk_component() + put_link() + depth
decrement in there is exactly equivalent to what's done right
after the first walk_component(). Easy to verify and not at all
surprising, seeing that there we have just walked the last
component of nested symlink.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull the block after the if-else in the end of what used to be do-while
body into all branches there. We are almost done with the massage...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
If we get ERR_PTR() from get_link(), we are guaranteed to get err != 0
when we break out of do-while, so we are going to hit if (err) return err;
shortly after it. Pull that into the if (IS_ERR(s)) body.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
... and strip __always_inline from follow_link() - remaining callers
don't need that.
Now link_path_walk() recursion is a direct one.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
shares space with nameidata->next, walk_component() et.al. store
the struct path of symlink instead of returning it into a variable
passed by caller.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Split a piece of fs/namei.c:follow_link() that does obtaining the link
body into a separate function. follow_link() itself is converted to
calling get_link() and then doing the body traversal (if any).
The next step will expand follow_link() call in link_path_walk()
and this helps to keep the size down...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
a) instead of storing the symlink body (via nd_set_link()) and returning
an opaque pointer later passed to ->put_link(), ->follow_link() _stores_
that opaque pointer (into void * passed by address by caller) and returns
the symlink body. Returning ERR_PTR() on error, NULL on jump (procfs magic
symlinks) and pointer to symlink body for normal symlinks. Stored pointer
is ignored in all cases except the last one.
Storing NULL for opaque pointer (or not storing it at all) means no call
of ->put_link().
b) the body used to be passed to ->put_link() implicitly (via nameidata).
Now only the opaque pointer is. In the cases when we used the symlink body
to free stuff, ->follow_link() now should store it as opaque pointer in addition
to returning it.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
when we go for on-demand allocation of saved state in
link_path_walk(), we'll want nameidata to stay around
for all 3 calls of path_mountpoint().
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
that avoids having nameidata on stack during the calls of
->rmdir()/->unlink() and *two* of those during the calls
of ->rename().
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
it's a convenient helper, but we'll want to shift nameidata
down the call chain, so it won't be available there...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
With LOOKUP_FOLLOW we unlazy and return 1; without it we either
fail with ELOOP or, for O_PATH opens, succeed. No need to mix
those cases...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
When O_PATH is present, O_CREAT isn't, so symlink_ok is always equal to
(open_flags & O_PATH) && !(nd->flags & LOOKUP_FOLLOW).
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
No ->inode_follow_link() methods use the nameidata arg, and
it is about to become private to namei.c.
So remove from all inode_follow_link() functions.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
path_openat() jumps to the wrong place after do_tmpfile() - it has
already done path_cleanup() (as part of path_lookupat() called by
do_tmpfile()), so doing that again can lead to double fput().
Cc: stable@vger.kernel.org # v3.11+
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Fetching ->d_inode, verifying ->d_seq and finding d_is_negative() to
be true does *not* mean that inode we'd fetched had been NULL - that
holds only while ->d_seq is still unchanged.
Shift d_is_negative() checks into lookup_fast() prior to ->d_seq
verification.
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Tested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Calling unlazy_walk() in walk_component() and do_last() when we find
a symlink that needs to be followed doesn't acquire a reference to vfsmount.
That's fine when the symlink is on the same vfsmount as the parent directory
(which is almost always the case), but it's not always true - one _can_
manage to bind a symlink on top of something. And in such cases we end up
with excessive mntput().
Cc: stable@vger.kernel.org # since 2.6.39
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Make pathwalk use d_is_reg() rather than S_ISREG() to determine whether to
honour O_TRUNC. Since this occurs after complete_walk(), the dentry type
field cannot change and the inode pointer cannot change as we hold a ref on
the dentry, so this should be safe.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Where we have:
if (!dentry->d_inode || d_is_negative(dentry)) {
type constructions in pathwalk we should be able to eliminate the check of
d_inode and rely solely on the result of d_is_negative() or d_is_positive().
What we do have to take care to do is to read d_inode after calling a
d_is_xxx() typecheck function to get the barriering right.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
just make const char iname[] the last member and compare name->name with
name->iname instead of checking name->separate
We need to make sure that out-of-line name doesn't end up allocated adjacent
to struct filename refering to it; fortunately, it's easy to achieve - just
allocate that struct filename with one byte in ->iname[], so that ->iname[0]
will be inside the same object and thus have an address different from that
of out-of-line name [spotted by Boqun Feng <boqun.feng@gmail.com>]
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Convert the following where appropriate:
(1) S_ISLNK(dentry->d_inode) to d_is_symlink(dentry).
(2) S_ISREG(dentry->d_inode) to d_is_reg(dentry).
(3) S_ISDIR(dentry->d_inode) to d_is_dir(dentry). This is actually more
complicated than it appears as some calls should be converted to
d_can_lookup() instead. The difference is whether the directory in
question is a real dir with a ->lookup op or whether it's a fake dir with
a ->d_automount op.
In some circumstances, we can subsume checks for dentry->d_inode not being
NULL into this, provided we the code isn't in a filesystem that expects
d_inode to be NULL if the dirent really *is* negative (ie. if we're going to
use d_inode() rather than d_backing_inode() to get the inode pointer).
Note that the dentry type field may be set to something other than
DCACHE_MISS_TYPE when d_inode is NULL in the case of unionmount, where the VFS
manages the fall-through from a negative dentry to a lower layer. In such a
case, the dentry type of the negative union dentry is set to the same as the
type of the lower dentry.
However, if you know d_inode is not NULL at the call site, then you can use
the d_is_xxx() functions even in a filesystem.
There is one further complication: a 0,0 chardev dentry may be labelled
DCACHE_WHITEOUT_TYPE rather than DCACHE_SPECIAL_TYPE. Strictly, this was
intended for special directory entry types that don't have attached inodes.
The following perl+coccinelle script was used:
use strict;
my @callers;
open($fd, 'git grep -l \'S_IS[A-Z].*->d_inode\' |') ||
die "Can't grep for S_ISDIR and co. callers";
@callers = <$fd>;
close($fd);
unless (@callers) {
print "No matches\n";
exit(0);
}
my @cocci = (
'@@',
'expression E;',
'@@',
'',
'- S_ISLNK(E->d_inode->i_mode)',
'+ d_is_symlink(E)',
'',
'@@',
'expression E;',
'@@',
'',
'- S_ISDIR(E->d_inode->i_mode)',
'+ d_is_dir(E)',
'',
'@@',
'expression E;',
'@@',
'',
'- S_ISREG(E->d_inode->i_mode)',
'+ d_is_reg(E)' );
my $coccifile = "tmp.sp.cocci";
open($fd, ">$coccifile") || die $coccifile;
print($fd "$_\n") || die $coccifile foreach (@cocci);
close($fd);
foreach my $file (@callers) {
chomp $file;
print "Processing ", $file, "\n";
system("spatch", "--sp-file", $coccifile, $file, "--in-place", "--no-show-diff") == 0 ||
die "spatch failed";
}
[AV: overlayfs parts skipped]
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
In order to ensure that filenames are not released before the audit
subsystem is done with the strings there are a number of hacks built
into the fs and audit subsystems around getname() and putname(). To
say these hacks are "ugly" would be kind.
This patch removes the filename hackery in favor of a more
conventional reference count based approach. The diffstat below tells
most of the story; lots of audit/fs specific code is replaced with a
traditional reference count based approach that is easily understood,
even by those not familiar with the audit and/or fs subsystems.
CC: viro@zeniv.linux.org.uk
CC: linux-fsdevel@vger.kernel.org
Signed-off-by: Paul Moore <pmoore@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Enable recording of filenames in getname_kernel() and remove the
kludgy workaround in __audit_inode() now that we have proper filename
logging for kernel users.
CC: viro@zeniv.linux.org.uk
CC: linux-fsdevel@vger.kernel.org
Signed-off-by: Paul Moore <pmoore@redhat.com>
Reviewed-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
a) make it accept ERR_PTR() as filename (and return its PTR_ERR() in that case)
b) make it putname() the sucker in the end otherwise
simplifies life for callers...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
There are several areas in the kernel that create temporary filename
objects using the following pattern:
int func(const char *name)
{
struct filename *file = { .name = name };
...
return 0;
}
... which for the most part works okay, but it causes havoc within the
audit subsystem as the filename object does not persist beyond the
lifetime of the function. This patch converts all of these temporary
filename objects into proper filename objects using getname_kernel()
and putname() which ensure that the filename object persists until the
audit subsystem is finished with it.
Also, a special thanks to Al Viro, Guenter Roeck, and Sabrina Dubroca
for helping resolve a difficult kernel panic on boot related to a
use-after-free problem in kern_path_create(); the thread can be seen
at the link below:
* https://lkml.org/lkml/2015/1/20/710
This patch includes code that was either based on, or directly written
by Al in the above thread.
CC: viro@zeniv.linux.org.uk
CC: linux@roeck-us.net
CC: sd@queasysnail.net
CC: linux-fsdevel@vger.kernel.org
Signed-off-by: Paul Moore <pmoore@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
In preparation for expanded use in the kernel, make getname_kernel()
more useful by allowing it to handle any legal filename length.
Thanks to Guenter Roeck for his suggestion to substitute memcpy() for
strlcpy().
CC: linux@roeck-us.net
CC: viro@zeniv.linux.org.uk
CC: linux-fsdevel@vger.kernel.org
Signed-off-by: Paul Moore <pmoore@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull vfs pile #2 from Al Viro:
"Next pile (and there'll be one or two more).
The large piece in this one is getting rid of /proc/*/ns/* weirdness;
among other things, it allows to (finally) make nameidata completely
opaque outside of fs/namei.c, making for easier further cleanups in
there"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
coda_venus_readdir(): use file_inode()
fs/namei.c: fold link_path_walk() call into path_init()
path_init(): don't bother with LOOKUP_PARENT in argument
fs/namei.c: new helper (path_cleanup())
path_init(): store the "base" pointer to file in nameidata itself
make default ->i_fop have ->open() fail with ENXIO
make nameidata completely opaque outside of fs/namei.c
kill proc_ns completely
take the targets of /proc/*/ns/* symlinks to separate fs
bury struct proc_ns in fs/proc
copy address of proc_ns_ops into ns_common
new helpers: ns_alloc_inum/ns_free_inum
make proc_ns_operations work with struct ns_common * instead of void *
switch the rest of proc_ns_operations to working with &...->ns
netns: switch ->get()/->put()/->install()/->inum() to working with &net->ns
make mntns ->get()/->put()/->install()/->inum() work with &mnt_ns->ns
common object embedded into various struct ....ns
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>
All callers of path_init() proceed to do the identical cleanup when
they are done with nameidata. Don't open-code it...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull VFS fixes from Al Viro:
"A bunch of assorted fixes, most of them followups to overlayfs merge"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
ovl: initialize ->is_cursor
Return short read or 0 at end of a raw device, not EIO
isofs: don't bother with ->d_op for normal case
isofs_cmp(): we'll never see a dentry for . or ..
overlayfs: fix lockdep misannotation
ovl: fix check for cursor
overlayfs: barriers for opening upper-layer directory
rcu: Provide counterpart to rcu_dereference() for non-RCU situations
staging: android: logger: Fix log corruption regression
The man page for open(2) indicates that when O_CREAT is specified, the
'mode' argument applies only to future accesses to the file:
Note that this mode applies only to future accesses of the newly
created file; the open() call that creates a read-only file
may well return a read/write file descriptor.
The man page for open(2) implies that 'mode' is treated identically by
O_CREAT and O_TMPFILE.
O_TMPFILE, however, behaves differently:
int fd = open("/tmp", O_TMPFILE | O_RDWR, 0);
assert(fd == -1);
assert(errno == EACCES);
int fd = open("/tmp", O_TMPFILE | O_RDWR, 0600);
assert(fd > 0);
For O_CREAT, do_last() sets acc_mode to MAY_OPEN only:
if (*opened & FILE_CREATED) {
/* Don't check for write permission, don't truncate */
open_flag &= ~O_TRUNC;
will_truncate = false;
acc_mode = MAY_OPEN;
path_to_nameidata(path, nd);
goto finish_open_created;
}
But for O_TMPFILE, do_tmpfile() passes the full op->acc_mode to
may_open().
This patch lines up the behavior of O_TMPFILE with O_CREAT. After the
inode is created, may_open() is called with acc_mode = MAY_OPEN, in
do_tmpfile().
A different, but related glibc bug revealed the discrepancy:
https://sourceware.org/bugzilla/show_bug.cgi?id=17523
The glibc lazily loads the 'mode' argument of open() and openat() using
va_arg() only if O_CREAT is present in 'flags' (to support both the 2
argument and the 3 argument forms of open; same idea for openat()).
However, the glibc ignores the 'mode' argument if O_TMPFILE is in
'flags'.
On x86_64, for open(), it magically works anyway, as 'mode' is in
RDX when entering open(), and is still in RDX on SYSCALL, which is where
the kernel looks for the 3rd argument of a syscall.
But openat() is not quite so lucky: 'mode' is in RCX when entering the
glibc wrapper for openat(), while the kernel looks for the 4th argument
of a syscall in R10. Indeed, the syscall calling convention differs from
the regular calling convention in this respect on x86_64. So the kernel
sees mode = 0 when trying to use glibc openat() with O_TMPFILE, and
fails with EACCES.
Signed-off-by: Eric Rannaud <e@nanocritical.com>
Acked-by: Andy Lutomirski <luto@amacapital.net>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In an overlay directory that shadows an empty lower directory, say
/mnt/a/empty102, do:
touch /mnt/a/empty102/x
unlink /mnt/a/empty102/x
rmdir /mnt/a/empty102
It's actually harmless, but needs another level of nesting between
I_MUTEX_CHILD and I_MUTEX_NORMAL.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Tested-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This adds a new RENAME_WHITEOUT flag. This flag makes rename() create a
whiteout of source. The whiteout creation is atomic relative to the
rename.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Whiteout isn't actually a new file type, but is represented as a char
device (Linus's idea) with 0/0 device number.
This has several advantages compared to introducing a new whiteout file
type:
- no userspace API changes (e.g. trivial to make backups of upper layer
filesystem, without losing whiteouts)
- no fs image format changes (you can boot an old kernel/fsck without
whiteout support and things won't break)
- implementation is trivial
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
It's already duplicated in btrfs and about to be used in overlayfs too.
Move the sticky bit check to an inline helper and call the out-of-line
helper only in the unlikly case of the sticky bit being set.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
We need to be able to check inode permissions (but not filesystem implied
permissions) for stackable filesystems. Expose this interface for overlayfs.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Add a new inode operation i_op->dentry_open(). This is for stacked filesystems
that want to return a struct file from a different filesystem.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Pull vfs updates from Al Viro:
"The big thing in this pile is Eric's unmount-on-rmdir series; we
finally have everything we need for that. The final piece of prereqs
is delayed mntput() - now filesystem shutdown always happens on
shallow stack.
Other than that, we have several new primitives for iov_iter (Matt
Wilcox, culled from his XIP-related series) pushing the conversion to
->read_iter()/ ->write_iter() a bit more, a bunch of fs/dcache.c
cleanups and fixes (including the external name refcounting, which
gives consistent behaviour of d_move() wrt procfs symlinks for long
and short names alike) and assorted cleanups and fixes all over the
place.
This is just the first pile; there's a lot of stuff from various
people that ought to go in this window. Starting with
unionmount/overlayfs mess... ;-/"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (60 commits)
fs/file_table.c: Update alloc_file() comment
vfs: Deduplicate code shared by xattr system calls operating on paths
reiserfs: remove pointless forward declaration of struct nameidata
don't need that forward declaration of struct nameidata in dcache.h anymore
take dname_external() into fs/dcache.c
let path_init() failures treated the same way as subsequent link_path_walk()
fix misuses of f_count() in ppp and netlink
ncpfs: use list_for_each_entry() for d_subdirs walk
vfs: move getname() from callers to do_mount()
gfs2_atomic_open(): skip lookups on hashed dentry
[infiniband] remove pointless assignments
gadgetfs: saner API for gadgetfs_create_file()
f_fs: saner API for ffs_sb_create_file()
jfs: don't hash direct inode
[s390] remove pointless assignment of ->f_op in vmlogrdr ->open()
ecryptfs: ->f_op is never NULL
android: ->f_op is never NULL
nouveau: __iomem misannotations
missing annotation in fs/file.c
fs: namespace: suppress 'may be used uninitialized' warnings
...
As it is, path_lookupat() and path_mounpoint() might end up leaking struct file
reference in some cases.
Spotted-by: Eric Biggers <ebiggers3@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull security subsystem updates from James Morris.
Mostly ima, selinux, smack and key handling updates.
* 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security: (65 commits)
integrity: do zero padding of the key id
KEYS: output last portion of fingerprint in /proc/keys
KEYS: strip 'id:' from ca_keyid
KEYS: use swapped SKID for performing partial matching
KEYS: Restore partial ID matching functionality for asymmetric keys
X.509: If available, use the raw subjKeyId to form the key description
KEYS: handle error code encoded in pointer
selinux: normalize audit log formatting
selinux: cleanup error reporting in selinux_nlmsg_perm()
KEYS: Check hex2bin()'s return when generating an asymmetric key ID
ima: detect violations for mmaped files
ima: fix race condition on ima_rdwr_violation_check and process_measurement
ima: added ima_policy_flag variable
ima: return an error code from ima_add_boot_aggregate()
ima: provide 'ima_appraise=log' kernel option
ima: move keyring initialization to ima_init()
PKCS#7: Handle PKCS#7 messages that contain no X.509 certs
PKCS#7: Better handling of unsupported crypto
KEYS: Overhaul key identification when searching for asymmetric keys
KEYS: Implement binary asymmetric key ID handling
...
Now that d_invalidate can no longer fail, stop returning a useless
return code. For the few callers that checked the return code update
remove the handling of d_invalidate failure.
Reviewed-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
With the introduction of mount namespaces and bind mounts it became
possible to access files and directories that on some paths are mount
points but are not mount points on other paths. It is very confusing
when rm -rf somedir returns -EBUSY simply because somedir is mounted
somewhere else. With the addition of user namespaces allowing
unprivileged mounts this condition has gone from annoying to allowing
a DOS attack on other users in the system.
The possibility for mischief is removed by updating the vfs to support
rename, unlink and rmdir on a dentry that is a mountpoint and by
lazily unmounting mountpoints on deleted dentries.
In particular this change allows rename, unlink and rmdir system calls
on a dentry without a mountpoint in the current mount namespace to
succeed, and it allows rename, unlink, and rmdir performed on a
distributed filesystem to update the vfs cache even if when there is a
mount in some namespace on the original dentry.
There are two common patterns of maintaining mounts: Mounts on trusted
paths with the parent directory of the mount point and all ancestory
directories up to / owned by root and modifiable only by root
(i.e. /media/xxx, /dev, /dev/pts, /proc, /sys, /sys/fs/cgroup/{cpu,
cpuacct, ...}, /usr, /usr/local). Mounts on unprivileged directories
maintained by fusermount.
In the case of mounts in trusted directories owned by root and
modifiable only by root the current parent directory permissions are
sufficient to ensure a mount point on a trusted path is not removed
or renamed by anyone other than root, even if there is a context
where the there are no mount points to prevent this.
In the case of mounts in directories owned by less privileged users
races with users modifying the path of a mount point are already a
danger. fusermount already uses a combination of chdir,
/proc/<pid>/fd/NNN, and UMOUNT_NOFOLLOW to prevent these races. The
removable of global rename, unlink, and rmdir protection really adds
nothing new to consider only a widening of the attack window, and
fusermount is already safe against unprivileged users modifying the
directory simultaneously.
In principle for perfect userspace programs returning -EBUSY for
unlink, rmdir, and rename of dentires that have mounts in the local
namespace is actually unnecessary. Unfortunately not all userspace
programs are perfect so retaining -EBUSY for unlink, rmdir and rename
of dentries that have mounts in the current mount namespace plays an
important role of maintaining consistency with historical behavior and
making imperfect userspace applications hard to exploit.
v2: Remove spurious old_dentry.
v3: Optimized shrink_submounts_and_drop
Removed unsued afs label
v4: Simplified the changes to check_submounts_and_drop
Do not rename check_submounts_and_drop shrink_submounts_and_drop
Document what why we need atomicity in check_submounts_and_drop
Rely on the parent inode mutex to make d_revalidate and d_invalidate
an atomic unit.
v5: Refcount the mountpoint to detach in case of simultaneous
renames.
Reviewed-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
In preparation for allowing mountpoints to be renamed and unlinked
in remote filesystems and in other mount namespaces test if on a dentry
there is a mount in the local mount namespace before allowing it to
be renamed or unlinked.
The primary motivation here are old versions of fusermount unmount
which is not safe if the a path can be renamed or unlinked while it is
verifying the mount is safe to unmount. More recent versions are simpler
and safer by simply using UMOUNT_NOFOLLOW when unmounting a mount
in a directory owned by an arbitrary user.
Miklos Szeredi <miklos@szeredi.hu> reports this is approach is good
enough to remove concerns about new kernels mixed with old versions
of fusermount.
A secondary motivation for restrictions here is that it removing empty
directories that have non-empty mount points on them appears to
violate the rule that rmdir can not remove empty directories. As
Linus Torvalds pointed out this is useful for programs (like git) that
test if a directory is empty with rmdir.
Therefore this patch arranges to enforce the existing mount point
semantics for local mount namespace.
v2: Rewrote the test to be a drop in replacement for d_mountpoint
v3: Use bool instead of int as the return type of is_local_mountpoint
Reviewed-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Commit d6bb3e9075 ("vfs: simplify and shrink stack frame of
link_path_walk()") introduced build problems with GCC versions older
than 4.6 due to the initialisation of a member of an anonymous union in
struct qstr without enclosing braces.
This hits GCC bug 10676 [1] (which was fixed in GCC 4.6 by [2]), and
causes the following build error:
fs/namei.c: In function 'link_path_walk':
fs/namei.c:1778: error: unknown field 'hash_len' specified in initializer
This is worked around by adding explicit braces.
[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=10676
[2] https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=159206
Fixes: d6bb3e9075 (vfs: simplify and shrink stack frame of link_path_walk())
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-metag@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit 9226b5b440 ("vfs: avoid non-forwarding large load after small
store in path lookup") made link_path_walk() always access the
"hash_len" field as a single 64-bit entity, in order to avoid mixed size
accesses to the members.
However, what I didn't notice was that that effectively means that the
whole "struct qstr this" is now basically redundant. We already
explicitly track the "const char *name", and if we just use "u64
hash_len" instead of "long len", there is nothing else left of the
"struct qstr".
We do end up wanting the "struct qstr" if we have a filesystem with a
"d_hash()" function, but that's a rare case, and we might as well then
just squirrell away the name and hash_len at that point.
End result: fewer live variables in the loop, a smaller stack frame, and
better code generation. And we don't need to pass in pointers variables
to helper functions any more, because the return value contains all the
relevant information. So this removes more lines than it adds, and the
source code is clearer too.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull vfs fixes from Al Viro:
"double iput() on failure exit in lustre, racy removal of spliced
dentries from ->s_anon in __d_materialise_dentry() plus a bunch of
assorted RCU pathwalk fixes"
The RCU pathwalk fixes end up fixing a couple of cases where we
incorrectly dropped out of RCU walking, due to incorrect initialization
and testing of the sequence locks in some corner cases. Since dropping
out of RCU walk mode forces the slow locked accesses, those corner cases
slowed down quite dramatically.
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
be careful with nd->inode in path_init() and follow_dotdot_rcu()
don't bugger nd->seq on set_root_rcu() from follow_dotdot_rcu()
fix bogus read_seqretry() checks introduced in b37199e
move the call of __d_drop(anon) into __d_materialise_unique(dentry, anon)
[fix] lustre: d_make_root() does iput() on dentry allocation failure
The performance regression that Josef Bacik reported in the pathname
lookup (see commit 99d263d4c5 "vfs: fix bad hashing of dentries") made
me look at performance stability of the dcache code, just to verify that
the problem was actually fixed. That turned up a few other problems in
this area.
There are a few cases where we exit RCU lookup mode and go to the slow
serializing case when we shouldn't, Al has fixed those and they'll come
in with the next VFS pull.
But my performance verification also shows that link_path_walk() turns
out to have a very unfortunate 32-bit store of the length and hash of
the name we look up, followed by a 64-bit read of the combined hash_len
field. That screws up the processor store to load forwarding, causing
an unnecessary hickup in this critical routine.
It's caused by the ugly calling convention for the "hash_name()"
function, and easily fixed by just making hash_name() fill in the whole
'struct qstr' rather than passing it a pointer to just the hash value.
With that, the profile for this function looks much smoother.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
in the former we simply check if dentry is still valid after picking
its ->d_inode; in the latter we fetch ->d_inode in the same places
where we fetch dentry and its ->d_seq, under the same checks.
Cc: stable@vger.kernel.org # 2.6.38+
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
return the value instead, and have path_init() do the assignment. Broken by
"vfs: Fix absolute RCU path walk failures due to uninitialized seq number",
which was Cc-stable with 2.6.38+ as destination. This one should go where
it went.
To avoid dummy value returned in case when root is already set (it would do
no harm, actually, since the only caller that doesn't ignore the return value
is guaranteed to have nd->root *not* set, but it's more obvious that way),
lift the check into callers. And do the same to set_root(), to keep them
in sync.
Cc: stable@vger.kernel.org # 2.6.38+
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Josef Bacik found a performance regression between 3.2 and 3.10 and
narrowed it down to commit bfcfaa77bd ("vfs: use 'unsigned long'
accesses for dcache name comparison and hashing"). He reports:
"The test case is essentially
for (i = 0; i < 1000000; i++)
mkdir("a$i");
On xfs on a fio card this goes at about 20k dir/sec with 3.2, and 12k
dir/sec with 3.10. This is because we spend waaaaay more time in
__d_lookup on 3.10 than in 3.2.
The new hashing function for strings is suboptimal for <
sizeof(unsigned long) string names (and hell even > sizeof(unsigned
long) string names that I've tested). I broke out the old hashing
function and the new one into a userspace helper to get real numbers
and this is what I'm getting:
Old hash table had 1000000 entries, 0 dupes, 0 max dupes
New hash table had 12628 entries, 987372 dupes, 900 max dupes
We had 11400 buckets with a p50 of 30 dupes, p90 of 240 dupes, p99 of 567 dupes for the new hash
My test does the hash, and then does the d_hash into a integer pointer
array the same size as the dentry hash table on my system, and then
just increments the value at the address we got to see how many
entries we overlap with.
As you can see the old hash function ended up with all 1 million
entries in their own bucket, whereas the new one they are only
distributed among ~12.5k buckets, which is why we're using so much
more CPU in __d_lookup".
The reason for this hash regression is two-fold:
- On 64-bit architectures the down-mixing of the original 64-bit
word-at-a-time hash into the final 32-bit hash value is very
simplistic and suboptimal, and just adds the two 32-bit parts
together.
In particular, because there is no bit shuffling and the mixing
boundary is also a byte boundary, similar character patterns in the
low and high word easily end up just canceling each other out.
- the old byte-at-a-time hash mixed each byte into the final hash as it
hashed the path component name, resulting in the low bits of the hash
generally being a good source of hash data. That is not true for the
word-at-a-time case, and the hash data is distributed among all the
bits.
The fix is the same in both cases: do a better job of mixing the bits up
and using as much of the hash data as possible. We already have the
"hash_32|64()" functions to do that.
Reported-by: Josef Bacik <jbacik@fb.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Empty files and missing xattrs do not guarantee that a file was
just created. This patch passes FILE_CREATED flag to IMA to
reliably identify new files.
Signed-off-by: Dmitry Kasatkin <d.kasatkin@samsung.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: <stable@vger.kernel.org> 3.14+
Looks like the directory loop check is actually done in renameat?
Whatever, leave this out rather than trying to keep it up to date with
the code.
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
In REF-walk mode, ->d_manage can return -EISDIR to indicate
that the dentry is not really a mount trap (or even a mount point)
and that any mounts or any DCACHE_NEED_AUTOMOUNT flag should be
ignored.
RCU-walk mode doesn't currently support this, so if there is a dentry
with DCACHE_NEED_AUTOMOUNT set but which shouldn't be a mount-trap,
lookup_fast() will always drop in REF-walk mode.
With this patch, an -EISDIR from ->d_manage will always cause mounts
and automounts to be ignored, both in REF-walk and RCU-walk.
Bug-fixed-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Ian Kent <raven@themaw.net>
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Christoph Hellwig suggests:
1) make vfs_rename call ->rename2 if it exists instead of ->rename
2) switch all filesystems that you're adding NOREPLACE support for to
use ->rename2
3) see how many ->rename instances we'll have left after a few
iterations of 2.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Currently umount on symlink blocks following umount:
/vz is separate mount
# ls /vz/ -al | grep test
drwxr-xr-x. 2 root root 4096 Jul 19 01:14 testdir
lrwxrwxrwx. 1 root root 11 Jul 19 01:16 testlink -> /vz/testdir
# umount -l /vz/testlink
umount: /vz/testlink: not mounted (expected)
# lsof /vz
# umount /vz
umount: /vz: device is busy. (unexpected)
In this case mountpoint_last() gets an extra refcount on path->mnt
Signed-off-by: Vasily Averin <vvs@openvz.org>
Acked-by: Ian Kent <raven@themaw.net>
Acked-by: Jeff Layton <jlayton@primarydata.com>
Cc: stable@vger.kernel.org
Signed-off-by: Christoph Hellwig <hch@lst.de>
The kernel has no concept of capabilities with respect to inodes; inodes
exist independently of namespaces. For example, inode_capable(inode,
CAP_LINUX_IMMUTABLE) would be nonsense.
This patch changes inode_capable to check for uid and gid mappings and
renames it to capable_wrt_inode_uidgid, which should make it more
obvious what it does.
Fixes CVE-2014-4014.
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Serge Hallyn <serge.hallyn@ubuntu.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: stable@vger.kernel.org
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
in non-lazy walk we need to be careful about dentry switching from
negative to positive - both ->d_flags and ->d_inode are updated,
and in some places we might see only one store. The cases where
dentry has been obtained by dcache lookup with ->i_mutex held on
parent are safe - ->d_lock and ->i_mutex provide all the barriers
we need. However, there are several places where we run into
trouble:
* do_last() fetches ->d_inode, then checks ->d_flags and
assumes that inode won't be NULL unless d_is_negative() is true.
Race with e.g. creat() - we might have fetched the old value of
->d_inode (still NULL) and new value of ->d_flags (already not
DCACHE_MISS_TYPE). Lin Ming has observed and reported the resulting
oops.
* a bunch of places checks ->d_inode for being non-NULL,
then checks ->d_flags for "is it a symlink". Race with symlink(2)
in case if our CPU sees ->d_inode update first - we see non-NULL
there, but ->d_flags still contains DCACHE_MISS_TYPE instead of
DCACHE_SYMLINK_TYPE. Result: false negative on "should we follow
link here?", with subsequent unpleasantness.
Cc: stable@vger.kernel.org # 3.13 and 3.14 need that one
Reported-and-tested-by: Lin Ming <minggr@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull vfs updates from Al Viro:
"The first vfs pile, with deep apologies for being very late in this
window.
Assorted cleanups and fixes, plus a large preparatory part of iov_iter
work. There's a lot more of that, but it'll probably go into the next
merge window - it *does* shape up nicely, removes a lot of
boilerplate, gets rid of locking inconsistencie between aio_write and
splice_write and I hope to get Kent's direct-io rewrite merged into
the same queue, but some of the stuff after this point is having
(mostly trivial) conflicts with the things already merged into
mainline and with some I want more testing.
This one passes LTP and xfstests without regressions, in addition to
usual beating. BTW, readahead02 in ltp syscalls testsuite has started
giving failures since "mm/readahead.c: fix readahead failure for
memoryless NUMA nodes and limit readahead pages" - might be a false
positive, might be a real regression..."
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (63 commits)
missing bits of "splice: fix racy pipe->buffers uses"
cifs: fix the race in cifs_writev()
ceph_sync_{,direct_}write: fix an oops on ceph_osdc_new_request() failure
kill generic_file_buffered_write()
ocfs2_file_aio_write(): switch to generic_perform_write()
ceph_aio_write(): switch to generic_perform_write()
xfs_file_buffered_aio_write(): switch to generic_perform_write()
export generic_perform_write(), start getting rid of generic_file_buffer_write()
generic_file_direct_write(): get rid of ppos argument
btrfs_file_aio_write(): get rid of ppos
kill the 5th argument of generic_file_buffered_write()
kill the 4th argument of __generic_file_aio_write()
lustre: don't open-code kernel_recvmsg()
ocfs2: don't open-code kernel_recvmsg()
drbd: don't open-code kernel_recvmsg()
constify blk_rq_map_user_iov() and friends
lustre: switch to kernel_sendmsg()
ocfs2: don't open-code kernel_sendmsg()
take iov_iter stuff to mm/iov_iter.c
process_vm_access: tidy up a bit
...
Pull file locking updates from Jeff Layton:
"Highlights:
- maintainership change for fs/locks.c. Willy's not interested in
maintaining it these days, and is OK with Bruce and I taking it.
- fix for open vs setlease race that Al ID'ed
- cleanup and consolidation of file locking code
- eliminate unneeded BUG() call
- merge of file-private lock implementation"
* 'locks-3.15' of git://git.samba.org/jlayton/linux:
locks: make locks_mandatory_area check for file-private locks
locks: fix locks_mandatory_locked to respect file-private locks
locks: require that flock->l_pid be set to 0 for file-private locks
locks: add new fcntl cmd values for handling file private locks
locks: skip deadlock detection on FL_FILE_PVT locks
locks: pass the cmd value to fcntl_getlk/getlk64
locks: report l_pid as -1 for FL_FILE_PVT locks
locks: make /proc/locks show IS_FILE_PVT locks as type "FLPVT"
locks: rename locks_remove_flock to locks_remove_file
locks: consolidate checks for compatible filp->f_mode values in setlk handlers
locks: fix posix lock range overflow handling
locks: eliminate BUG() call when there's an unexpected lock on file close
locks: add __acquires and __releases annotations to locks_start and locks_stop
locks: remove "inline" qualifier from fl_link manipulation functions
locks: clean up comment typo
locks: close potential race between setlease and open
MAINTAINERS: update entry for fs/locks.c
