[10/99] futex: Check for NULL keys in match_futex

[Greg KH]

2.6.31-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Darren Hart <dvhltc@xxxxxxxxxx>

commit 2bc872036e1c5948b5b02942810bbdd8dbdb9812 upstream.

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@xxxxxxxxxx>
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>
LKML-Reference: <4AD60687.10306@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

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

--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -150,7 +150,8 @@ static struct futex_hash_bucket *hash_fu
  */
 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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