pidns: use task_active_pid_ns in do_notify_parent (32084504) · Commits · 戴 / test

Using task_active_pid_ns is more robust because it works even after we have called exit_namespaces. This change allows us to have parent processes that are zombies. Normally a zombie parent processes is crazy and the last thing you would want to have but in the case of not letting the init process of a pid namespace be reaped until all of it's children are dead and reaped a zombie parent process is exactly what we want. Signed-off-by:

Eric W. Biederman <ebiederm@xmission.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Cyrill Gorcunov <gorcunov@openvz.org> Cc: Louis Rilling <louis.rilling@kerlabs.com> Cc: Mike Galbraith <efault@gmx.de> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

kernel/signal.c

+5 −6

Original line number	Diff line number	Diff line
		@@ -1656,19 +1656,18 @@ bool do_notify_parent(struct task_struct *tsk, int sig)
		info.si_signo = sig;
		info.si_errno = 0;
		/*
		* we are under tasklist_lock here so our parent is tied to
		* us and cannot exit and release its namespace.
		* We are under tasklist_lock here so our parent is tied to
		* us and cannot change.
		*
		* the only it can is to switch its nsproxy with sys_unshare,
		* bu uncharing pid namespaces is not allowed, so we'll always
		* see relevant namespace
		* task_active_pid_ns will always return the same pid namespace
		* until a task passes through release_task.
		*
		* write_lock() currently calls preempt_disable() which is the
		* same as rcu_read_lock(), but according to Oleg, this is not
		* correct to rely on this
		*/
		rcu_read_lock();
		info.si_pid = task_pid_nr_ns(tsk, tsk->parent->nsproxy->pid_ns);
		info.si_pid = task_pid_nr_ns(tsk, task_active_pid_ns(tsk->parent));
		info.si_uid = from_kuid_munged(task_cred_xxx(tsk->parent, user_ns),
		task_uid(tsk));
		rcu_read_unlock();

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