linux-kernel - [ 24/70] futex: Test for pi_mutex on fault in futex_wait_requeue

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Message-Id: <20120807032759.521009923@decadent.org.uk>
Date:	Tue, 07 Aug 2012 04:28:19 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Darren Hart <dvhart@...ux.intel.com>,
	Dave Jones <davej@...hat.com>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [ 24/70] futex: Test for pi_mutex on fault in futex_wait_requeue_pi()

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Darren Hart <dvhart@...ux.intel.com>

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@...ux.intel.com>
Cc: Dave Jones <davej@...hat.com>
Cc: Dan Carpenter <dan.carpenter@...cle.com>
Link: http://lkml.kernel.org/r/dc59890338fc413606f04e5c5b131530734dae3d.1342809673.git.dvhart@linux.intel.com
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 kernel/futex.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index e2b0fb9..05018bf 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2370,7 +2370,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
 	 * 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)
 			rt_mutex_unlock(pi_mutex);
 	} else if (ret == -EINTR) {
 		/*


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