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signalfd: use wake_up_pollfree()

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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: Linus Torvalds <torvalds@linux-foundation.org>
Fixes: d80e731eca ("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: Eric Biggers <ebiggers@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Eric Biggers 2021-12-08 17:04:53 -08:00 committed by Greg Kroah-Hartman
parent 9f3acee7ea
commit fc2f636ffc
1 changed files with 1 additions and 11 deletions
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12
fs/signalfd.c
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@ -35,17 +35,7 @@
void signalfd_cleanup(struct sighand_struct *sighand) void signalfd_cleanup(struct sighand_struct *sighand)
{ {
wait_queue_head_t *wqh = &sighand->signalfd_wqh; wake_up_pollfree(&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);
} }
struct signalfd_ctx { struct signalfd_ctx {