From: Eric Biggers <ebiggers@xxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxxx>
Fixes: d80e731ecab4 ("epoll: introduce POLLFREE to flush ->signalfd_wqh before kfree()")
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20211209010455.42744-4-ebiggers@xxxxxxxxxx
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/signalfd.c | 12 +-----------
1 file changed, 1 insertion(+), 11 deletions(-)
--- 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 {
