drm/virtio: don't leak bo on drm_gem_object_init failure

Reported-by: 李强 <liqiang6-s@360.cn>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170406155941.458-1-kraxel@redhat.com

CVE-2017-10810

(cherry picked from commit 385aee96)
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Seth Forshee <seth.forshee@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

drivers/gpu/drm/virtio/virtgpu_object.c

@@ -81,8 +81,10 @@ int virtio_gpu_object_create(struct virtio_gpu_device *vgdev,
 		return -ENOMEM;
 	size = roundup(size, PAGE_SIZE);
 	ret = drm_gem_object_init(vgdev->ddev, &bo->gem_base, size);
-	if (ret != 0)
+	if (ret != 0) {
+		kfree(bo);
 		return ret;
+	}
 	bo->dumb = false;
 	virtio_gpu_init_ttm_placement(bo, pinned);