linux-kernel - [PATCH 0/3] pidns: Closing the pid namespace exit race.

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Message-ID: <87havs7rvv.fsf_-_@xmission.com>
Date:	Sun, 06 May 2012 17:32:20 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Pavel Emelyanov <xemul@...allels.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Louis Rilling <louis.rilling@...labs.com>,
	Mike Galbraith <efault@....de>
Subject: [PATCH 0/3] pidns: Closing the pid namespace exit race.

I had some patches that broke the circular reference between the
pid_namespace and the proc_mnt by combining the reference counts but the
world has changes and now the proc_mnt reference count is not suitable
to be used that way so that plan is scrapped.

I did play with it and I have found a relatively elegant way of at least
handling the problem of self reaping children escaping from
zap_pid_ns_processess.

The following patches guarantee that the task with pid == 1 will be the
last task reaped in a pid namespace. Making proc_flush_task safe.

The previous patch to call pid_ns_release_proc on fork failure is still
needed.  These patches simply address the other failure mode.

How did it escape my memory that setting SIGCHLD to SIG_IGN caused
children to autoreap?

Eric W. Biederman (3):
      pidns:  Use task_active_pid_ns in do_notify_parent.
      pidns: Guarantee that the pidns init will be the last pidns process reaped.
      pidns: Make killed children autoreap

 kernel/exit.c          |   46 +++++++++++++++++++++++++++++++++++-----------
 kernel/pid_namespace.c |    7 ++++++-
 kernel/signal.c        |   11 +++++------
 3 files changed, 46 insertions(+), 18 deletions(-)
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