!5579 mm: ksm: fix use-after-free kasan report in ksm_might_need_to_copy

Merge Pull Request from: @ci-robot 
 
PR sync from: Jinjiang Tu <tujinjiang@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/A4DB7GG5VMYKIR3MORLLXNDUYSUXQJSO/ 
 
https://gitee.com/openeuler/kernel/issues/I9BWES 
 
Link:https://gitee.com/openeuler/kernel/pulls/5579

 

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