[PATCH] futex: check for NULL keys in match_futex

[Darren Hart]

From: Darren Hart <dvhltc@xxxxxxxxxx>

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@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
CC: Eric Dumazet <eric.dumazet@xxxxxxxxx>
CC: Dinakar Guniguntala <dino@xxxxxxxxxx>
CC: John Stultz <johnstul@xxxxxxxxxx>
---

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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