Commit 447c19f3 authored by Pavel Begunkov's avatar Pavel Begunkov Committed by Jens Axboe
Browse files

io_uring: fix ltout double free on completion race 



Always remove linked timeout on io_link_timeout_fn() from the master
request link list, otherwise we may get use-after-free when first
io_link_timeout_fn() puts linked timeout in the fail path, and then
will be found and put on master's free.

Cc: stable@vger.kernel.org # 5.10+
Fixes: 90cd7e42 ("io_uring: track link timeout's master explicitly")
Reported-and-tested-by: default avatar <syzbot+5a864149dd970b546223@syzkaller.appspotmail.com>
Signed-off-by: default avatarPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/69c46bf6ce37fec4fdcd98f0882e18eb07ce693a.1620990121.git.asml.silence@gmail.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent a298232e

fs/io_uring.c

+4 −3
Original line number Diff line number Diff line
@@ -6354,10 +6354,11 @@ static enum hrtimer_restart io_link_timeout_fn(struct hrtimer *timer) 
	 * We don't expect the list to be empty, that will only happen if we

	 * race with the completion of the linked work.

	 */

	if (prev && req_ref_inc_not_zero(prev))

	if (prev) {

		io_remove_next_linked(prev);

	else

		if (!req_ref_inc_not_zero(prev))

			prev = NULL;

	}

	spin_unlock_irqrestore(&ctx->completion_lock, flags);



	if (prev) {