On Wed, Mar 02, 2022 at 03:11:21PM +0100, Stefano Garzarella wrote: > On Wed, Mar 02, 2022 at 08:35:08AM -0500, Michael S. Tsirkin wrote: > > On Wed, Mar 02, 2022 at 10:34:46AM +0100, Stefano Garzarella wrote: > > > On Wed, Mar 02, 2022 at 07:54:21AM +0000, Lee Jones wrote: > > > > vhost_vsock_handle_tx_kick() already holds the mutex during its call > > > > to vhost_get_vq_desc(). All we have to do is take the same lock > > > > during virtqueue clean-up and we mitigate the reported issues. > > > > > > > > Link: https://syzkaller.appspot.com/bug?extid=279432d30d825e63ba00 > > > > > > This issue is similar to [1] that should be already fixed upstream by [2]. > > > > > > However I think this patch would have prevented some issues, because > > > vhost_vq_reset() sets vq->private to NULL, preventing the worker from > > > running. > > > > > > Anyway I think that when we enter in vhost_dev_cleanup() the worker should > > > be already stopped, so it shouldn't be necessary to take the mutex. But in > > > order to prevent future issues maybe it's better to take them, so: > > > > > > Reviewed-by: Stefano Garzarella <sgarzare@xxxxxxxxxx> > > > > > > [1] > > > https://syzkaller.appspot.com/bug?id=993d8b5e64393ed9e6a70f9ae4de0119c605a822 > > > [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a58da53ffd70294ebea8ecd0eb45fd0d74add9f9 > > > > > > Right. I want to queue this but I would like to get a warning > > so we can detect issues like [2] before they cause more issues. > > I agree, what about moving the warning that we already have higher up, right > at the beginning of the function? > > I mean something like this: > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index 59edb5a1ffe2..1721ff3f18c0 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -692,6 +692,8 @@ void vhost_dev_cleanup(struct vhost_dev *dev) > { > int i; > + WARN_ON(!llist_empty(&dev->work_list)); > + > for (i = 0; i < dev->nvqs; ++i) { > if (dev->vqs[i]->error_ctx) > eventfd_ctx_put(dev->vqs[i]->error_ctx); > @@ -712,7 +714,6 @@ void vhost_dev_cleanup(struct vhost_dev *dev) > dev->iotlb = NULL; > vhost_clear_msg(dev); > wake_up_interruptible_poll(&dev->wait, EPOLLIN | EPOLLRDNORM); > - WARN_ON(!llist_empty(&dev->work_list)); > if (dev->worker) { > kthread_stop(dev->worker); > dev->worker = NULL; > Hmm I'm not sure why it matters. > And maybe we can also check vq->private and warn in the loop, because the > work_list may be empty if the device is doing nothing. > > Thanks, > Stefano
