vmwgfx: information leak in vmw_execbuf_copy_fence_user()

If ret is non-zero then we don't initialize the struct which leaks
stack information to user space.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Vasiliy Kulikov <segoon@openwall.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c

@@ -1070,6 +1070,8 @@ vmw_execbuf_copy_fence_user(struct vmw_private *dev_priv,
 	if (user_fence_rep == NULL)
 		return;
 
+	memset(&fence_rep, 0, sizeof(fence_rep));
+
 	fence_rep.error = ret;
 	if (ret == 0) {
 		BUG_ON(fence == NULL);