!5478 jfs: fix array-index-out-of-bounds in diNewExt

Merge Pull Request from: @ci-robot 
 
PR sync from: Long Li <leo.lilong@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/TTX3XTUGZI4TDK5473OAFV356LUHMEBS/ 
 
https://gitee.com/src-openeuler/kernel/issues/I96G7F 
 
Link:https://gitee.com/openeuler/kernel/pulls/5478

 

Reviewed-by: Liu YongQiang <liuyongqiang13@huawei.com>
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>