Re: [PATCH net] vhost: correctly remove wait queue during poll failure

[Darren Kenny]

Hi Jason,

On Tue, Mar 27, 2018 at 11:47:22AM +0800, Jason Wang wrote:
> We tried to remove vq poll from wait queue, but do not check whether
> or not it was in a list before. This will lead double free. Fixing
> this by checking poll->wqh to make sure it was in a list.

This text seems at odds with the code below, instead of checking
poll-whq, you are removing that check...

Maybe the text needs rewording?

Thanks,

Darren.

> Reported-by: syzbot+c0272972b01b872e604a@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: 2b8b328b61c79 ("vhost_net: handle polling errors when setting backend")
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> ---
> drivers/vhost/vhost.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 1b3e8d2d..5d5a9d9 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -212,8 +212,7 @@ int vhost_poll_start(struct vhost_poll *poll, struct file *file)
> 	if (mask)
> 		vhost_poll_wakeup(&poll->wait, 0, 0, poll_to_key(mask));
> 	if (mask & EPOLLERR) {
> -		if (poll->wqh)
> -			remove_wait_queue(poll->wqh, &poll->wait);
> +		vhost_poll_stop(poll);
> 		ret = -EINVAL;
> 	}
>
> --
> 2.7.4