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futex: Validate waiter correctly in futex_proxy_trylock_atomic() 

The loop in futex_requeue() has a sanity check for the waiter, which is
missing in futex_proxy_trylock_atomic(). In theory the key2 check is
sufficient, but futexes are cursed so add it for completeness and paranoia
sake.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211305.193767519@linutronix.de
This commit is contained in:
Thomas Gleixner 2021-08-15 23:29:04 +02:00 committed by Ingo Molnar
parent c49f7ece46
commit dc7109aaa2
1 changed files with 7 additions and 0 deletions
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7
kernel/futex.c
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@ -1879,6 +1879,13 @@ futex_proxy_trylock_atomic(u32 __user *pifutex, struct futex_hash_bucket *hb1,
if (!top_waiter)
return 0;
/*
* Ensure that this is a waiter sitting in futex_wait_requeue_pi()
* and waiting on the 'waitqueue' futex which is always !PI.
*/
if (!top_waiter->rt_waiter || top_waiter->pi_state)
ret = -EINVAL;
/* Ensure we requeue to the expected futex. */
if (!match_futex(top_waiter->requeue_pi_key, key2))
return -EINVAL;