Re: [Qemu-devel] [PATCH] virtio: validate the existence of handle_output before calling it

[Don Koch]

On Thu, 12 Feb 2015 11:05:17 +0800
Jason Wang <address@hidden> wrote:

> We don't validate the existence of handle_output which may let a buggy
> guest to trigger a SIGSEV easily. Fix this by validate its existence
> before.
> 
> Cc: address@hidden
> Cc: Anthony Liguori <address@hidden>
> Cc: Michael S. Tsirkin <address@hidden>
> Signed-off-by: Jason Wang <address@hidden>
> ---
>  hw/virtio/virtio.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index d735343..ffc22e8 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -761,6 +761,10 @@ void virtio_queue_notify_vq(VirtQueue *vq)
>  {
>      if (vq->vring.desc) {
>          VirtIODevice *vdev = vq->vdev;
> +
> +        if (!vq->handle_output) {
> +            return;
> +        }

Maybe better to just change line 762 to:
     if (vq->vring.desc && vq->handle_output) {

-d

>          trace_virtio_queue_notify(vdev, vq - vdev->vq, vq);
>          vq->handle_output(vdev, vq);
>      }
> -- 
> 1.9.1
> 
>