Commit 9537bae0 authored by Eric Biggers's avatar Eric Biggers

signalfd: use wake_up_pollfree()

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.orgSigned-off-by: default avatarEric Biggers <ebiggers@google.com>
parent a880b28a
......@@ -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 {
......
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