Re: [PATCH] io_uring: fail poll arm on queue proc failure

[Stefano Garzarella <sgarzare@redhat.com>]

On Tue, Aug 11, 2020 at 09:52:55AM -0600, Jens Axboe wrote:
> 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
> Signed-off-by: Jens Axboe <axboe@kernel.dk>

LGTM:
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

Stefano

> 
> ---
> 
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index 99582cf5106b..8a2afd8c33c9 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -4883,7 +4883,7 @@ static bool io_arm_poll_handler(struct io_kiocb *req)
>  
>  	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);
>  		kfree(apoll->double_poll);
> -- 
> Jens Axboe
>