!5339 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/ISGXAYLUYQ6CLF56SWADT65X5N6GA2IV/ 
 
https://gitee.com/src-openeuler/kernel/issues/I99JWJ 
 
Link:https://gitee.com/openeuler/kernel/pulls/5339

 

Reviewed-by: Xu Kuohai <xukuohai@huawei.com>
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com>