move exit_task_namespaces() outside of exit_notify()
exit_notify() does exit_task_namespaces() after forget_original_parent(). This was needed to ensure that ->nsproxy can't be cleared prematurely, an exiting child we are going to reparent can do do_notify_parent() and use the parent's (ours) pid_ns. However, after 32084504 "pidns: use task_active_pid_ns in do_notify_parent" ->nsproxy != NULL is no longer needed, we rely on task_active_pid_ns(). Move exit_task_namespaces() from exit_notify() to do_exit(), after exit_fs() and before exit_task_work(). This solves the problem reported by Andrey, free_ipc_ns()->shm_destroy() does fput() which needs task_work_add(). Note: this particular problem can be fixed if we change fput(), and that change makes sense anyway. But there is another reason to move the callsite. The original reason for exit_task_namespaces() from the middle of exit_notify() was subtle and it has already gone away, now this looks confusing. And this allows us do simplify exit_notify(), we can avoid unlock/lock(tasklist) and we can use ->exit_state instead of PF_EXITING in forget_original_parent(). Reported-by: NAndrey Vagin <avagin@openvz.org> Signed-off-by: NOleg Nesterov <oleg@redhat.com> Acked-by: N"Eric W. Biederman" <ebiederm@xmission.com> Acked-by: NAndrey Vagin <avagin@openvz.org> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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