From: Eric Biggers <ebiggers@kernel.org>
To: Alexander Viro <viro@zeniv.linux.org.uk>,
Benjamin LaHaise <bcrl@kvack.org>
Cc: linux-aio@kvack.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, Ramji Jiyani <ramjiyani@google.com>,
Christoph Hellwig <hch@lst.de>,
Linus Torvalds <torvalds@linux-foundation.org>,
Oleg Nesterov <oleg@redhat.com>, Jens Axboe <axboe@kernel.dk>,
Martijn Coenen <maco@android.com>,
stable@vger.kernel.org
Subject: [PATCH v2 3/5] signalfd: use wake_up_pollfree()
Date: Tue, 7 Dec 2021 01:57:24 -0800 [thread overview]
Message-ID: <20211207095726.169766-4-ebiggers@kernel.org> (raw)
In-Reply-To: <20211207095726.169766-1-ebiggers@kernel.org>
From: Eric Biggers <ebiggers@google.com>
wake_up_poll() uses nr_exclusive=1, so it's not guaranteed to wake up
all non-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: d80e731ecab4 ("epoll: introduce POLLFREE to flush ->signalfd_wqh before kfree()")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
fs/signalfd.c | 12 +-----------
1 file changed, 1 insertion(+), 11 deletions(-)
diff --git a/fs/signalfd.c b/fs/signalfd.c
index 040e1cf905282..65ce0e72e7b95 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 {
--
2.34.1
next prev parent reply other threads:[~2021-12-07 9:59 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-07 9:57 [PATCH v2 0/5] aio: fix use-after-free and missing wakeups Eric Biggers
2021-12-07 9:57 ` [PATCH v2 1/5] wait: add wake_up_pollfree() Eric Biggers
2021-12-07 9:57 ` [PATCH v2 2/5] binder: use wake_up_pollfree() Eric Biggers
2021-12-07 19:11 ` Eric Biggers
2021-12-07 9:57 ` Eric Biggers [this message]
2021-12-07 9:57 ` [PATCH v2 4/5] aio: keep poll requests on waitqueue until completed Eric Biggers
2021-12-07 9:57 ` [PATCH v2 5/5] aio: fix use-after-free due to missing POLLFREE handling Eric Biggers
2021-12-07 11:17 ` [PATCH v2 0/5] aio: fix use-after-free and missing wakeups Christoph Hellwig
2021-12-07 19:10 ` Eric Biggers
2021-12-07 23:24 ` Linus Torvalds
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