linux-kernel - [PATCH] futex: check for NULL keys in match

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Date:	Wed, 14 Oct 2009 10:12:39 -0700
From:	Darren Hart <dvhltc@...ibm.com>
To:	"lkml, " <linux-kernel@...r.kernel.org>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Dinakar Guniguntala <dino@...ibm.com>,
	John Stultz <johnstul@...ux.vnet.ibm.com>
Subject: [PATCH] futex: check for NULL keys in match_futex

From: Darren Hart <dvhltc@...ibm.com>

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().  This results in cleaner code than checking at each call
site.  While match_futex(NULL, NULL) returning false is a little odd, it
will OOPS as it is today.  This approach catches all possible call sites
as well.

Signed-off-by: Darren Hart <dvhltc@...ibm.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
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>
---

 kernel/futex.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index 4949d33..5971730 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);
 }
-- 
Darren Hart
IBM Linux Technology Center
Real-Time Linux Team
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