linux-kernel - Re: [PATCH 2/4] pid_ns: (BUG 11391) change ->child_reaper when init->group

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Message-ID: <20080827003524.GA22580@us.ibm.com>
Date:	Tue, 26 Aug 2008 17:35:24 -0700
From:	sukadev@...ibm.com
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Pavel Emelyanov <xemul@...nvz.org>,
	Robert Rex <robert.rex@...sol.com>,
	Roland McGrath <roland@...hat.com>,
	Serge Hallyn <serue@...ibm.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] pid_ns: (BUG 11391) change ->child_reaper when
	init->group_leader exits

sukadev@...ibm.com [sukadev@...ibm.com] wrote:
| I was able to repro the problem without the patchset and could  not
| reproduce  with the patchset. But just had a quick question while
| reviewing the patches.
| 
| Oleg Nesterov [oleg@...sign.ru] wrote:
| | We don't change pid_ns->child_reaper when the main thread of the
| | subnamespace init exits. As Robert Rex <robert.rex@...sol.com>
| | pointed out this is wrong.
| | 
| | Yes, the re-parenting itself works correctly, but if the reparented
| | task exits it needs ->parent->nsproxy->pid_ns in do_notify_parent(),
| 
| If the task was reparented, then with patch 1/4 its parent would be
| the global init (init_pid_ns.child_reaper) right ?
| 
| | and if the main thread is zombie its ->nsproxy was already cleared
| | by exit_task_namespaces().
| 
| If above is true, then even if the main thread's nsproxy is NULL, does
| it affect the reparented task ?

never mind. I see it now. The group_dead check in current code is not
sufficient (and the zap_pid_ns() may not have been called when main
thread is exiting).
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