• Oleg Nesterov's avatar
    move exit_task_namespaces() outside of exit_notify() · 8aac6270
    Oleg Nesterov authored
    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: default avatarAndrey Vagin <avagin@openvz.org>
    Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
    Acked-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
    Acked-by: default avatarAndrey Vagin <avagin@openvz.org>
    Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
    8aac6270
exit.c 42.8 KB