linux-kernel - [tip:core/urgent] futex: Check for NULL keys in match

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Date:	Wed, 14 Oct 2009 20:11:03 GMT
From:	tip-bot for Darren Hart <dvhltc@...ibm.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, dvhltc@...ibm.com, hpa@...or.com,
	mingo@...hat.com, eric.dumazet@...il.com, johnstul@...ibm.com,
	peterz@...radead.org, dino@...ibm.com, tglx@...utronix.de,
	mingo@...e.hu
Subject: [tip:core/urgent] futex: Check for NULL keys in match_futex

Commit-ID:  2bc872036e1c5948b5b02942810bbdd8dbdb9812
Gitweb:     http://git.kernel.org/tip/2bc872036e1c5948b5b02942810bbdd8dbdb9812
Author:     Darren Hart <dvhltc@...ibm.com>
AuthorDate: Wed, 14 Oct 2009 10:12:39 -0700
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Wed, 14 Oct 2009 22:00:14 +0200

futex: Check for NULL keys in match_futex

If userspace tries to perform a requeue_pi on a non-requeue_pi waiter,
it will find the futex_q->requeue_pi_key to be NULL and OOPS.

Check for NULL in match_futex() instead of doing explicit NULL pointer
checks on all call sites.  While match_futex(NULL, NULL) returning
false is a little odd, it's still correct as we expect valid key
references.

Signed-off-by: Darren Hart <dvhltc@...ibm.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...e.hu>
CC: Eric Dumazet <eric.dumazet@...il.com>
CC: Dinakar Guniguntala <dino@...ibm.com>
CC: John Stultz <johnstul@...ibm.com>
Cc: stable@...nel.org
LKML-Reference: <4AD60687.10306@...ibm.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 kernel/futex.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index 5c88839..06938e5 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -150,7 +150,8 @@ static struct futex_hash_bucket *hash_futex(union futex_key *key)
  */
 static inline int match_futex(union futex_key *key1, union futex_key *key2)
 {
-	return (key1->both.word == key2->both.word
+	return (key1 && key2
+		&& key1->both.word == key2->both.word
 		&& key1->both.ptr == key2->both.ptr
 		&& key1->both.offset == key2->both.offset);
 }
--
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