!2050 memcg: fix a UAF problem in drain_all_stock()

Merge Pull Request from: @ci-robot 
 
PR sync from: "GONG, Ruiqi" <gongruiqi1@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/OJJHRD2ODSO4FEMQ2XHNLCBJLB3EHNQG/ 
 
https://gitee.com/openeuler/kernel/issues/I7Z1ZU 
 
Link:https://gitee.com/openeuler/kernel/pulls/2050

 

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