!5336 binder: fix race between mmput() and do_exit()

Merge Pull Request from: @ci-robot 
 
PR sync from: Zheng Yejian <zhengyejian1@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/QHCW5AE5JVX3B44XCA3TGY7OIGE7TAQV/ 
 
https://gitee.com/src-openeuler/kernel/issues/I99JWJ 
 
Link:https://gitee.com/openeuler/kernel/pulls/5336

 

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