From: Sebastian Andrzej Siewior Date: Wed, 1 Jul 2026 13:11:50 +0000 (+0200) Subject: futex/requeue: Revert "Prevent NULL pointer dereference in remove_waiter() on self... X-Git-Tag: v7.2-rc2~3^2 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=39def6d250d370298f86c116f4ac60093cefadaa;p=thirdparty%2Flinux.git futex/requeue: Revert "Prevent NULL pointer dereference in remove_waiter() on self-deadlock"" The commit cited below should not have been merged. It attemted to fix an existing problem ansd thereby introduced new problems by keeping the pi_state in state Q_REQUEUE_PI_IN_PROGRESS and leaking it. Based on the commit description the intention was to handle the case when task_blocks_on_rt_mutex() returns -EDEADLK and the following remove_waiter() dereferences the NULL pointer in waiter->task. That is already handled by Davidlohr in commit 40a25d59e85b3 ("locking/rtmutex: Skip remove_waiter() when waiter is not enqueued") and requires no further acting. Revert the commit breaking the "waiter == owner" case again. Fixes: 74e144274af39 ("futex/requeue: Prevent NULL pointer dereference in remove_waiter() on self-deadlock") Reported-by: Michael Bommarito Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260701131150.0Ijhq4Dw@linutronix.de Closes: https://lore.kernel.org/all/20260629020049.2082397-1-michael.bommarito@gmail.com --- diff --git a/kernel/futex/requeue.c b/kernel/futex/requeue.c index 7384672916fb..79823ad13683 100644 --- a/kernel/futex/requeue.c +++ b/kernel/futex/requeue.c @@ -645,12 +645,6 @@ retry_private: continue; } - /* Self-deadlock: non-top waiter already owns the PI futex. */ - if (rt_mutex_owner(&pi_state->pi_mutex) == this->task) { - ret = -EDEADLK; - break; - } - ret = rt_mutex_start_proxy_lock(&pi_state->pi_mutex, this->rt_waiter, this->task);