[v2.6.34-stable 202/213] futex: Test for pi_mutex on fault in futex_wait_requeue_pi()

From: Paul Gortmaker
Date: Wed Feb 05 2014 - 15:11:32 EST

From: Darren Hart <dvhart@xxxxxxxxxxxxxxx>

This is a commit scheduled for the next v2.6.34 longterm release.
If you see a problem with using this for longterm, please comment.

commit b6070a8d9853eda010a549fa9a09eb8d7269b929 upstream.

If fixup_pi_state_owner() faults, pi_mutex may be NULL. Test
for pi_mutex != NULL before testing the owner against current
and possibly unlocking it.

Signed-off-by: Darren Hart <dvhart@xxxxxxxxxxxxxxx>
Cc: Dave Jones <davej@xxxxxxxxxx>
Cc: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/dc59890338fc413606f04e5c5b131530734dae3d.1342809673.git.dvhart@xxxxxxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
kernel/futex.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index d4e7f0ea1f94..0e8043833223 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2348,7 +2348,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, int fshared,
* fault, unlock the rt_mutex and return the fault to userspace.
if (ret == -EFAULT) {
- if (rt_mutex_owner(pi_mutex) == current)
+ if (pi_mutex && rt_mutex_owner(pi_mutex) == current)
} else if (ret == -EINTR) {

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