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author | Al Viro <viro@zeniv.linux.org.uk> | 2019-08-03 11:51:18 -0400 |
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committer | Ben Hutchings <ben@decadent.org.uk> | 2019-12-10 18:01:20 +0000 |
commit | 9c64678adf6713cb86d5111c534f2d40805f0502 (patch) | |
tree | e0f8c341cfeacf9a64a2a5dc3a1733293e10af4c /arch/powerpc | |
parent | 0d589fdceb28b3d39523d1dd0d4ad959efb57d0f (diff) | |
download | linux-stable-9c64678adf6713cb86d5111c534f2d40805f0502.tar.gz linux-stable-9c64678adf6713cb86d5111c534f2d40805f0502.tar.bz2 linux-stable-9c64678adf6713cb86d5111c534f2d40805f0502.zip |
configfs: fix a deadlock in configfs_symlink()
commit 351e5d869e5ac10cb40c78b5f2d7dfc816ad4587 upstream.
Configfs abuses symlink(2). Unlike the normal filesystems, it
wants the target resolved at symlink(2) time, like link(2) would've
done. The problem is that ->symlink() is called with the parent
directory locked exclusive, so resolving the target inside the
->symlink() is easily deadlocked.
Short of really ugly games in sys_symlink() itself, all we can
do is to unlock the parent before resolving the target and
relock it after. However, that invalidates the checks done
by the caller of ->symlink(), so we have to
* check that dentry is still where it used to be
(it couldn't have been moved, but it could've been unhashed)
* recheck that it's still negative (somebody else
might've successfully created a symlink with the same name
while we were looking the target up)
* recheck the permissions on the parent directory.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@lst.de>
[bwh: Backported to 3.16: open-code inode_{,un}lock()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'arch/powerpc')
0 files changed, 0 insertions, 0 deletions