!4249 ubifs: fix possible dereference after free

Merge Pull Request from: @ci-robot 
 
PR sync from: ZhaoLong Wang <wangzhaolong1@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/X5JG3L7DKIXMAZSQ7WVDFEFGREGWBTIO/ 
 
https://gitee.com/openeuler/kernel/issues/I8ZCT1 
 
Link:https://gitee.com/openeuler/kernel/pulls/4249

 

Reviewed-by: Zheng Zengkai <zhengzengkai@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>