vhost-user-gpu: fix memory disclosure in virgl_cmd_get_capset_info (CVE-2021-3545)

Otherwise some of the 'resp' will be leaked to guest.

Fixes: CVE-2021-3545
Reported-by: Li Qiang <liq3ea@163.com>
virtio-gpu fix: 42a8dadc ("virtio-gpu: fix information leak
in getting capset info dispatch")

Signed-off-by: Li Qiang <liq3ea@163.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20210516030403.107723-2-liq3ea@163.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

contrib/vhost-user-gpu/virgl.c

@@ -128,6 +128,7 @@ virgl_cmd_get_capset_info(VuGpu *g,
 
     VUGPU_FILL_CMD(info);
 
+    memset(&resp, 0, sizeof(resp));
     if (info.capset_index == 0) {
         resp.capset_id = VIRTIO_GPU_CAPSET_VIRGL;
         virgl_renderer_get_cap_set(resp.capset_id,