Commit Graph

823 Commits

Author SHA1 Message Date
Trond Myklebust daf3761c9f namei: results of d_is_negative() should be checked after dentry revalidation
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>
2015-10-10 10:17:27 -07:00
Masanari Iida 2a78b857d3 namei: fix warning while make xmldocs caused by namei.c
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>
2015-09-10 13:29:01 -07:00
Eric W. Biederman 397d425dc2 vfs: Test for and handle paths that are unreachable from their mnt_root
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>
2015-08-21 03:20:10 -04:00
Al Viro aa65fa35ba may_follow_link() should use nd->inode
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>
2015-08-04 23:23:50 -04:00
Al Viro 97242f99a0 link_path_walk(): be careful when failing with ENOTDIR
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>
2015-08-01 20:18:38 -04:00
Al Viro 06d7137e5c namei: make set_root_rcu() return void
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>
2015-06-29 12:07:04 -04:00
Al Viro b853a16176 turn user_{path_at,path,lpath,path_dir}() into static inlines
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-15 01:10:45 -04:00
Al Viro 9883d1855e namei: move saved_nd pointer into struct nameidata
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>
2015-05-15 01:10:45 -04:00
Al Viro 520ae68747 inline user_path_create()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-15 01:10:44 -04:00
Al Viro a2ec4a2d5c inline user_path_parent()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-15 01:10:44 -04:00
Al Viro 76ae2a5ab1 namei: trim do_last() arguments
now that struct filename is stashed in nameidata we have no need to
pass it in

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-15 01:10:43 -04:00
Al Viro c8a53ee5ee namei: stash dfd and name into nameidata
fewer arguments to pass around...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-15 01:10:43 -04:00
Al Viro 102b8af266 namei: fold path_cleanup() into terminate_walk()
they are always called next to each other; moreover,
terminate_walk() is more symmetrical that way.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-15 01:10:42 -04:00
Al Viro 5c31b6cedb namei: saner calling conventions for filename_parentat()
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>
2015-05-15 01:10:42 -04:00
Al Viro 181c37b6e4 namei: saner calling conventions for filename_create()
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>
2015-05-15 01:10:42 -04:00
Al Viro 391172c46e namei: shift nameidata down into filename_parentat()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-15 01:10:41 -04:00
Al Viro abc9f5beb1 namei: make filename_lookup() reject ERR_PTR() passed as name
makes for much easier life in callers

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-15 01:10:41 -04:00
Al Viro 9ad1aaa615 namei: shift nameidata inside filename_lookup()
pass root instead; non-NULL => copy to nd.root and
set LOOKUP_ROOT in flags

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-15 01:10:40 -04:00
Al Viro e4bd1c1a95 namei: move putname() call into filename_lookup()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-15 01:10:40 -04:00
Al Viro 625b6d1054 namei: pass the struct path to store the result down into path_lookupat()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-15 01:10:39 -04:00
Al Viro 18d8c86011 namei: uninline set_root{,_rcu}()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-15 01:10:39 -04:00
Al Viro aed434ada6 namei: be careful with mountpoint crossings in follow_dotdot_rcu()
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>
2015-05-15 01:10:38 -04:00
Al Viro 5a8d87e8ed namei: unlazy_walk() doesn't need to mess with current->fs anymore
now that we have ->root_seq, legitimize_path(&nd->root, nd->root_seq)
will do just fine...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-15 01:10:36 -04:00
Al Viro 8f47a0167c namei: handle absolute symlinks without dropping out of RCU mode
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-15 01:10:22 -04:00
Al Viro 8c1b456689 enable passing fast relative symlinks without dropping out of RCU mode
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-15 01:06:28 -04:00
NeilBrown 8fa9dd2466 VFS/namei: make the use of touch_atime() in get_link() RCU-safe.
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>
2015-05-15 01:06:27 -04:00
Al Viro bc40aee053 namei: don't unlazy until get_link()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-15 01:06:27 -04:00
Al Viro 7973387a2f namei: make unlazy_walk and terminate_walk handle nd->stack, add unlazy_link
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>
2015-05-15 01:06:01 -04:00
Al Viro 0450b2d120 namei: store seq numbers in nd->stack[]
we'll need them for unlazy_walk()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-11 08:13:14 -04:00
Al Viro 31956502dd namei: make may_follow_link() safe in RCU mode
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>
2015-05-11 08:13:13 -04:00
Al Viro 6548fae2ec namei: make put_link() RCU-safe
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>
2015-05-11 08:13:13 -04:00
Al Viro 5f2c4179e1 switch ->put_link() from dentry to inode
only one instance looks at that argument at all; that sole
exception wants inode rather than dentry.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-11 08:13:12 -04:00
NeilBrown bda0be7ad9 security: make inode_follow_link RCU-walk aware
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>
2015-05-11 08:13:11 -04:00
Al Viro 181548c051 namei: pick_link() callers already have inode
no need to refetch (and once we move unlazy out of there, recheck ->d_seq).

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-11 08:13:10 -04:00
David Howells 63afdfc781 VFS: Handle lower layer dentry/inode in pathwalk
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>
2015-05-11 08:13:10 -04:00
Al Viro 237d8b327a namei: store inode in nd->stack[]
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-11 08:13:09 -04:00
Al Viro 254cf58212 namei: don't mangle nd->seq in lookup_fast()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-11 08:13:09 -04:00
Al Viro 6e9918b7b3 namei: explicitly pass seq number to unlazy_walk() when dentry != NULL
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-11 08:13:09 -04:00
Al Viro 3595e2346c link_path_walk: use explicit returns for failure exits
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-11 08:13:08 -04:00
Al Viro deb106c632 namei: lift terminate_walk() all the way up
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>
2015-05-11 08:13:08 -04:00
Al Viro 3bdba28b72 namei: lift link_path_walk() call out of trailing_symlink()
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>
2015-05-11 08:12:57 -04:00
Al Viro 368ee9ba56 namei: path_init() calling conventions change
* 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>
2015-05-11 08:10:41 -04:00
Al Viro 34a26b99b7 namei: get rid of nameidata->base
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>
2015-05-11 08:05:05 -04:00
Al Viro 8bcb77fabd namei: split off filename_lookupat() with LOOKUP_PARENT
new functions: filename_parentat() and path_parentat() resp.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-10 22:20:20 -04:00
Al Viro b5cd339762 namei: may_follow_link() - lift terminate_walk() on failures into caller
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-10 22:20:20 -04:00
Al Viro ab10492345 namei: take increment of nd->depth into pick_link()
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>
2015-05-10 22:20:19 -04:00
Al Viro 1cf2665b5b namei: kill nd->link
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>
2015-05-10 22:20:19 -04:00
Al Viro fec2fa24e8 may_follow_link(): trim arguments
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-10 22:20:18 -04:00
Al Viro cd179f4468 namei: move bumping the refcount of link->mnt into pick_link()
update the failure cleanup in may_follow_link() to match that.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-10 22:20:18 -04:00
Al Viro e8bb73dfb0 namei: fold put_link() into the failure case of complete_walk()
... 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>
2015-05-10 22:20:17 -04:00