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Message-Id: <20211211001926.100856-4-ebiggers@kernel.org>
Date: Fri, 10 Dec 2021 16:19:26 -0800
From: Eric Biggers <ebiggers@...nel.org>
To: stable@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 4.14 v2 3/3] signalfd: use wake_up_pollfree()
From: Eric Biggers <ebiggers@...gle.com>
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@...ux-foundation.org>
Fixes: d80e731ecab4 ("epoll: introduce POLLFREE to flush ->signalfd_wqh before kfree()")
Cc: stable@...r.kernel.org
Link: https://lore.kernel.org/r/20211209010455.42744-4-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
---
fs/signalfd.c | 12 +-----------
1 file changed, 1 insertion(+), 11 deletions(-)
diff --git a/fs/signalfd.c b/fs/signalfd.c
index 1c667af86da52..0b7c6c2c95b89 100644
--- a/fs/signalfd.c
+++ b/fs/signalfd.c
@@ -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, POLLHUP | POLLFREE);
+ wake_up_pollfree(&sighand->signalfd_wqh);
}
struct signalfd_ctx {
--
2.34.1
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