From: Trond Myklebust <Trond.Myklebust@netapp.com>
Date: Fri, 31 Mar 2006 10:30:55 +0000 (-0800)
Subject: [PATCH] fs/locks.c: Fix sys_flock() race
X-Git-Tag: v2.6.17-rc1~79
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=993dfa8776308dcfd311cf77a3bbed4aa11e9868;p=pandora-kernel.git

[PATCH] fs/locks.c: Fix sys_flock() race

sys_flock() currently has a race which can result in a double free in the
multi-thread case.

Thread 1			Thread 2

sys_flock(file, LOCK_EX)
				sys_flock(file, LOCK_UN)

If Thread 2 removes the lock from inode->i_lock before Thread 1 tests for
list_empty(&lock->fl_link) at the end of sys_flock, then both threads will
end up calling locks_free_lock for the same lock.

Fix is to make flock_lock_file() do the same as posix_lock_file(), namely
to make a copy of the request, so that the caller can always free the lock.

This also has the side-effect of fixing up a reference problem in the
lockd handling of flock.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

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