Re: [Qemu-devel] [PATCH v2 for-1.6 1/2] hw/virtio/virtio: Don't allow guests to add/remove queues

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Jul 26, 2013 at 04:41:27PM +0100, Peter Maydell wrote:
> A queue size of 0 is used to indicate a nonexistent queue, so
> don't allow the guest to flip a queue between zero-size and
> non-zero-size. Don't permit setting of negative queue sizes
> either.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>


Reviewed-by: Michael S. Tsirkin <mst@redhat.com>

> ---
>  hw/virtio/virtio.c |   12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 09f62c6..60653f7 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -673,10 +673,16 @@ hwaddr virtio_queue_get_addr(VirtIODevice *vdev, int n)
>  
>  void virtio_queue_set_num(VirtIODevice *vdev, int n, int num)
>  {
> -    if (num <= VIRTQUEUE_MAX_SIZE) {
> -        vdev->vq[n].vring.num = num;
> -        virtqueue_init(&vdev->vq[n]);
> +    /* Don't allow guest to flip queue between existent and
> +     * nonexistent states, or to set it to an invalid size.
> +     */
> +    if (!!num != !!vdev->vq[n].vring.num ||
> +        num > VIRTQUEUE_MAX_SIZE ||
> +        num < 0) {
> +        return;
>      }
> +    vdev->vq[n].vring.num = num;
> +    virtqueue_init(&vdev->vq[n]);
>  }
>  
>  int virtio_queue_get_num(VirtIODevice *vdev, int n)
> -- 
> 1.7.9.5