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  1. 28 2月, 2016 4 次提交
  3. 23 1月, 2016 1 次提交
    • A
      wrappers for ->i_mutex access · 5955102c
      由 Al Viro 提交于 
      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: NAl Viro <viro@zeniv.linux.org.uk>
      5955102c
  5. 09 1月, 2016 1 次提交
    • N
      nfsd: don't hold i_mutex over userspace upcalls · bbddca8e
      由 NeilBrown 提交于 
      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: NNeilBrown <neilb@suse.de>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      bbddca8e
  7. 04 1月, 2016 1 次提交
  9. 31 12月, 2015 1 次提交
  11. 09 12月, 2015 3 次提交
    • A
      teach page_get_link() to work in RCU mode · d3883d4f
      由 Al Viro 提交于 
      more or less along the lines of Neil's patchset, sans the insanity
around kmap().
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      d3883d4f
    • A
      replace ->follow_link() with new method that could stay in RCU mode · 6b255391
      由 Al Viro 提交于 
      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: NAl Viro <viro@zeniv.linux.org.uk>
      6b255391
    • A
      don't put symlink bodies in pagecache into highmem · 21fc61c7
      由 Al Viro 提交于 
      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: NAl Viro <viro@zeniv.linux.org.uk>
      21fc61c7
  13. 07 12月, 2015 7 次提交
  15. 07 11月, 2015 1 次提交
  17. 28 10月, 2015 1 次提交
    • D
      namei: permit linking with CAP_FOWNER in userns · f2ca3796
      由 Dirk Steinmetz 提交于 
      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 23adbe12 ("fs,userns: Change
inode_capable to capable_wrt_inode_uidgid").
Signed-off-by: NDirk 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: NSeth Forshee <seth.forshee@canonical.com>
Signed-off-by: NEric W. Biederman <ebiederm@xmission.com>
      f2ca3796
  19. 11 10月, 2015 1 次提交
    • T
      namei: results of d_is_negative() should be checked after dentry revalidation · daf3761c
      由 Trond Myklebust 提交于 
      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 766c4cbf"

Al Viro says:
 "What happens is that 766c4cbf 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 766c4cbf does (prior to
  ->d_seq validation) but only use the result in cases where we do not
  discard this dentry outright"
Reported-by: NLeandro Awa <lawa@nvidia.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=104911
Fixes: 766c4cbf ("namei: d_is_negative() should be checked...")
Tested-by: NLeandro Awa <lawa@nvidia.com>
Cc: stable@vger.kernel.org # v4.1+
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>
Acked-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      daf3761c
  21. 29 9月, 2015 1 次提交
  23. 11 9月, 2015 1 次提交
  25. 21 8月, 2015 1 次提交
    • E
      vfs: Test for and handle paths that are unreachable from their mnt_root · 397d425d
      由 Eric W. Biederman 提交于 
      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: N"Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      397d425d
  27. 05 8月, 2015 1 次提交
  29. 02 8月, 2015 1 次提交
    • A
      link_path_walk(): be careful when failing with ENOTDIR · 97242f99
      由 Al Viro 提交于 
      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 b18825a7 - 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: NAl Viro <viro@zeniv.linux.org.uk>
      97242f99
  31. 30 6月, 2015 1 次提交
  33. 15 5月, 2015 13 次提交