From 2d3d22332b684fa19f5bca994b307a317b84199b Mon Sep 17 00:00:00 2001 From: Light Hsieh Date: Thu, 24 Feb 2022 14:23:28 +0800 Subject: [PATCH] [ALPS06649447] signalfd: use wake_up_pollfree() wake_up_poll() uses nr_exclusive=1, so its 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 its very fragile. Thus, the new function wake_up_pollfree() has been introduced. Convert signalfd to use wake_up_pollfree(). MTK-Commit-Id: dcf842d697ef618d3a7fc36b466016bd9b70183c Reported-by: Linus Torvalds Fixes: d80e731ecab4 ("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 Signed-off-by: Light Hsieh CR-Id: ALPS06649447 Feature: Google Security Patch Change-Id: I9b25a4974c6333cff47d1c74982f1167d11765e3 --- fs/signalfd.c | 12 +----------- 1 file changed, 1 insertion(+), 11 deletions(-) diff --git a/fs/signalfd.c b/fs/signalfd.c index 3c40a3bf772c..94e0ae01db5c 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, EPOLLHUP | POLLFREE); + wake_up_pollfree(&sighand->signalfd_wqh); } struct signalfd_ctx {