Re: [PATCH net V2] vhost: correctly remove wait queue during poll failure

[Darren Kenny]

On Tue, Mar 27, 2018 at 08:50:52PM +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 switching to use vhost_poll_stop() which zeros poll->wqh after
> removing poll from waitqueue to make sure it won't be freed twice.
>
> Cc: Darren Kenny <darren.kenny@xxxxxxxxxx>
> Reported-by: syzbot+c0272972b01b872e604a@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: 2b8b328b61c79 ("vhost_net: handle polling errors when setting backend")
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>

Reviewed-by: Darren Kenny <darren.kenny@xxxxxxxxxx>

> ---
> Changes from V1:
> - tweak the commit log for to match the code
> ---
> 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