file locking fix for 3.2

From: J. Bruce Fields
Date: Sat Dec 24 2011 - 16:50:41 EST

Please pull the following change from the for-3.2 branch at:

git:// for-3.2

One small 3.2 regression in the file-locking code. Seems like an
unlikely bug (null dereference on kmalloc failure), but the fix is a


J. Bruce Fields (1):
locks: fix null dereference on lease-break failure path

fs/locks.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)

commit b67e18a8e3425725cc17cc7633bccb06fb3c9eda
Author: J. Bruce Fields <bfields@xxxxxxxxxx>
Date: Mon Dec 19 17:57:11 2011 -0500

locks: fix null dereference on lease-break failure path

Commit 778fc546f749c588aa2f6cd50215d2715c374252 "locks: fix tracking of
inprogress lease breaks" introduced a null dereference on failure to
allocate memory.

This means an open (without O_NONBLOCK set) on a file with a lease
applied (generally only done when Samba or nfsd (with v4) is running)
could crash if a kmalloc() fails.

Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>

diff --git a/fs/locks.c b/fs/locks.c
index 3b0d05d..96a487a 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1214,8 +1214,8 @@ int __break_lease(struct inode *inode, unsigned int mode)
if ((flock == NULL) || !IS_LEASE(flock))
goto out;

- if (!locks_conflict(flock, new_fl))
- goto out;
+ if (flock->fl_type == F_RDLCK && !want_write)
+ goto out; /* no conflict */

for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next)
if (fl->fl_owner == current->files)
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