Commit 68b11e8b authored by Pavel Begunkov's avatar Pavel Begunkov Committed by Jens Axboe
Browse files

io_uring: explicitly count entries for poll reqs 



If __io_queue_proc() fails to add a second poll entry, e.g. kmalloc()
failed, but it goes on with a third waitqueue, it may succeed and
overwrite the error status. Count the number of poll entries we added,
so we can set pt->error to zero at the beginning and find out when the
mentioned scenario happens.

Cc: stable@vger.kernel.org
Fixes: 18bceab1 ("io_uring: allow POLL_ADD with double poll_wait() users")
Signed-off-by: default avatarPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/9d6b9e561f88bcc0163623b74a76c39f712151c3.1626774457.git.asml.silence@gmail.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 1b48773f

fs/io_uring.c

+10 −6
Original line number Diff line number Diff line
@@ -4802,6 +4802,7 @@ IO_NETOP_FN(recv); 
struct io_poll_table {

	struct poll_table_struct pt;

	struct io_kiocb *req;

	int nr_entries;

	int error;

};
@@ -4995,11 +4996,11 @@ static void __io_queue_proc(struct io_poll_iocb *poll, struct io_poll_table *pt, 
	struct io_kiocb *req = pt->req;



	/*

	 * If poll->head is already set, it's because the file being polled

	 * uses multiple waitqueues for poll handling (eg one for read, one

	 * for write). Setup a separate io_poll_iocb if this happens.

	 * The file being polled uses multiple waitqueues for poll handling

	 * (e.g. one for read, one for write). Setup a separate io_poll_iocb

	 * if this happens.

	 */

	if (unlikely(poll->head)) {

	if (unlikely(pt->nr_entries)) {

		struct io_poll_iocb *poll_one = poll;



		/* already have a 2nd entry, fail a third attempt */
@@ -5027,7 +5028,7 @@ static void __io_queue_proc(struct io_poll_iocb *poll, struct io_poll_table *pt, 
		*poll_ptr = poll;

	}



	pt->error = 0;

	pt->nr_entries++;

	poll->head = head;



	if (poll->events & EPOLLEXCLUSIVE)
@@ -5104,9 +5105,12 @@ static __poll_t __io_arm_poll_handler(struct io_kiocb *req, 


	ipt->pt._key = mask;

	ipt->req = req;

	ipt->error = -EINVAL;

	ipt->error = 0;

	ipt->nr_entries = 0;



	mask = vfs_poll(req->file, &ipt->pt) & poll->events;

	if (unlikely(!ipt->nr_entries) && !ipt->error)

		ipt->error = -EINVAL;



	spin_lock_irq(&ctx->completion_lock);

	if (likely(poll->head)) {