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