Re: [PULL 02/23] vhost-user-gpu: fix resource leak in 'vg_resource_create_2d' (CVE-2021-3544)

[Peter Maydell]

On Thu, 27 May 2021 at 15:28, Gerd Hoffmann <kraxel@redhat.com> wrote:
>
> From: Li Qiang <liq3ea@163.com>
>
> Call 'vugbm_buffer_destroy' in error path to avoid resource leak.
>
> Fixes: CVE-2021-3544
> Reported-by: Li Qiang <liq3ea@163.com>
> Reviewed-by: Prasad J Pandit <pjp@fedoraproject.org>
> Signed-off-by: Li Qiang <liq3ea@163.com>
> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> Message-Id: <20210516030403.107723-3-liq3ea@163.com>
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  contrib/vhost-user-gpu/vhost-user-gpu.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/contrib/vhost-user-gpu/vhost-user-gpu.c 
> b/contrib/vhost-user-gpu/vhost-user-gpu.c
> index f73f292c9f72..b5e153d0d648 100644
> --- a/contrib/vhost-user-gpu/vhost-user-gpu.c
> +++ b/contrib/vhost-user-gpu/vhost-user-gpu.c
> @@ -349,6 +349,7 @@ vg_resource_create_2d(VuGpu *g,
>          g_critical("%s: resource creation failed %d %d %d",
>                     __func__, c2d.resource_id, c2d.width, c2d.height);
>          g_free(res);
> +        vugbm_buffer_destroy(&res->buffer);
>          cmd->error = VIRTIO_GPU_RESP_ERR_OUT_OF_MEMORY;
>          return;
>      }

Hi; Coverity reports this as a use-after-free: we free 'res'
and then on the next line we pass a pointer into this freed
memory to vugbm_buffer_destroy(), which dereferences it.
Probably the two lines should be in the other order ?

(CID 1453812)

thanks
-- PMM