Re: [Qemu-devel] [PATCH] display: virtio-gpu-3d: check virgl capabilities max_size

[Pankaj Gupta <pagupta@redhat.com>]

> 
> From: Prasad J Pandit <pjp@fedoraproject.org>
> 
> Virtio GPU device while processing 'VIRTIO_GPU_CMD_GET_CAPSET'
> command, retrieves the maximum capabilities size to fill in the
> response object. It continues to fill in capabilities even if
> retrieved 'max_size' is zero(0), thus resulting in OOB access.
> Add check to avoid it.
> 
> Reported-by: Zhenhao Hong <zhenhaohong@gmail.com>
> Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
> ---
>  hw/display/virtio-gpu-3d.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/display/virtio-gpu-3d.c b/hw/display/virtio-gpu-3d.c
> index 758d33a..fbfb39f 100644
> --- a/hw/display/virtio-gpu-3d.c
> +++ b/hw/display/virtio-gpu-3d.c
> @@ -371,11 +371,12 @@ static void virgl_cmd_get_capset(VirtIOGPU *g,
>      virgl_renderer_get_cap_set(gc.capset_id, &max_ver,
>                                 &max_size);
>      resp = g_malloc(sizeof(*resp) + max_size);
> -
> -    resp->hdr.type = VIRTIO_GPU_RESP_OK_CAPSET;
> -    virgl_renderer_fill_caps(gc.capset_id,
> -                             gc.capset_version,
> -                             (void *)resp->capset_data);
> +    if (max_size) {
> +        resp->hdr.type = VIRTIO_GPU_RESP_OK_CAPSET;
> +        virgl_renderer_fill_caps(gc.capset_id,
> +                                 gc.capset_version,
> +                                 (void *)resp->capset_data);
> +    }
>      virtio_gpu_ctrl_response(g, cmd, &resp->hdr, sizeof(*resp) + max_size);

Just one point here for 'max_size=0', do we don't require to set resp->hdr.type?
If yes,  other patch on list by 'Li Qiang' can also help to avoid sending garbage value.

>      g_free(resp);
>  }
> --
> 2.9.3
> 
> 
>