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Commit f226fdd8 authored by Eric Biggers's avatar Eric Biggers Committed by Greg Kroah-Hartman
Browse files

signalfd: use wake_up_pollfree() 



commit 9537bae0da1f8d1e2361ab6d0479e8af7824e160 upstream.

wake_up_poll() uses nr_exclusive=1, so it's not guaranteed to wake up
all exclusive waiters.  Yet, POLLFREE *must* wake up all waiters.  epoll
and aio poll are fortunately not affected by this, but it's very
fragile.  Thus, the new function wake_up_pollfree() has been introduced.

Convert signalfd to use wake_up_pollfree().

Reported-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Fixes: d80e731e ("epoll: introduce POLLFREE to flush ->signalfd_wqh before kfree()")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20211209010455.42744-4-ebiggers@kernel.org


Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 32288f50

fs/signalfd.c

+1 −11
Original line number Diff line number Diff line
@@ -35,17 +35,7 @@ 


void signalfd_cleanup(struct sighand_struct *sighand)

{

	wait_queue_head_t *wqh = &sighand->signalfd_wqh;

	/*

	 * The lockless check can race with remove_wait_queue() in progress,

	 * but in this case its caller should run under rcu_read_lock() and

	 * sighand_cachep is SLAB_TYPESAFE_BY_RCU, we can safely return.

	 */

	if (likely(!waitqueue_active(wqh)))

		return;



	/* wait_queue_entry_t->func(POLLFREE) should do remove_wait_queue() */

	wake_up_poll(wqh, EPOLLHUP | POLLFREE);

	wake_up_pollfree(&sighand->signalfd_wqh);

}



struct signalfd_ctx {