spotted by ASAN

Fixes: 81d8ccb1
Reported-by: Euler Robot <euler.robot@huawei.com>
Signed-off-by: Pan Nengyuan <pannengyuan@huawei.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1576805650-16380-1-git-send-email-pannengyuan@huawei.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>