The following commit has been merged into the locking/core branch of tip: Commit-ID: dc7109aaa233d83b573f75763a9f1ae207042a53 Gitweb: https://git.kernel.org/tip/dc7109aaa233d83b573f75763a9f1ae207042a53 Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx> AuthorDate: Sun, 15 Aug 2021 23:29:04 +02:00 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitterDate: Tue, 17 Aug 2021 19:05:36 +02:00 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@xxxxxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> Link: https://lore.kernel.org/r/20210815211305.193767519@xxxxxxxxxxxxx --- kernel/futex.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/kernel/futex.c b/kernel/futex.c index 21625cb..a1f27fd 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -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;
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