releases/5.7.16/io_uring-fail-poll-arm-on-queue-proc-failure.patch

From a36da65c46565d2527eec3efdb546251e38253fd Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Tue, 11 Aug 2020 09:50:19 -0600
Subject: io_uring: fail poll arm on queue proc failure

From: Jens Axboe <axboe@kernel.dk>

commit a36da65c46565d2527eec3efdb546251e38253fd upstream.

Check the ipt.error value, it must have been either cleared to zero or
set to another error than the default -EINVAL if we don't go through the
waitqueue proc addition. Just give up on poll at that point and return
failure, this will fallback to async work.

io_poll_add() doesn't suffer from this failure case, as it returns the
error value directly.

Cc: stable@vger.kernel.org # v5.7+
Reported-by: syzbot+a730016dc0bdce4f6ff5@syzkaller.appspotmail.com
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/io_uring.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4544,7 +4544,7 @@ static bool io_arm_poll_handler(struct i
 
 	ret = __io_arm_poll_handler(req, &apoll->poll, &ipt, mask,
 					io_async_wake);
-	if (ret) {
+	if (ret || ipt.error) {
 		io_poll_remove_double(req, apoll->double_poll);
 		spin_unlock_irq(&ctx->completion_lock);
 		memcpy(&req->work, &apoll->work, sizeof(req->work));