Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753277Ab2EaKdM (ORCPT ); Thu, 31 May 2012 06:33:12 -0400 Received: from mailhub.sw.ru ([195.214.232.25]:2650 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752124Ab2EaKdK (ORCPT ); Thu, 31 May 2012 06:33:10 -0400 Message-ID: <4FC748D3.8050606@parallels.com> Date: Thu, 31 May 2012 14:32:51 +0400 From: Pavel Emelyanov User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.1) Gecko/20120209 Thunderbird/10.0.1 MIME-Version: 1.0 To: Oleg Nesterov CC: Andrew Morton , Cyrill Gorcunov , "Eric W. Biederman" , Louis Rilling , Mike Galbraith , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 1/2] pidns: guarantee that the pidns init will be the last pidns process reaped References: <20120530175745.GA19327@redhat.com> <20120530181429.GA19989@redhat.com> <20120530181500.GA20130@redhat.com> In-Reply-To: <20120530181500.GA20130@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1715 Lines: 35 On 05/30/2012 10:15 PM, Oleg Nesterov wrote: > From: Eric W. Biederman > > Today we have a two-fold bug. Sometimes release_task on pid == 1 in a > pid namespace can run before other processes in a pid namespace have had > release task called. With the result that pid_ns_release_proc can be > called before the last proc_flus_task() is done using > upid->ns->proc_mnt, resulting in the use of a stale pointer. This same > set of circumstances can lead to waitpid(...) returning for a processes > started with clone(CLONE_NEWPID) before the every process in the pid > namespace has actually exited. > > To fix this modify zap_pid_ns_processess wait until all other processes > in the pid namespace have exited, even EXIT_DEAD zombies. > > The delay_group_leader and related tests ensure that the thread gruop > leader will be the last thread of a process group to be reaped, or to > become EXIT_DEAD and self reap. With the change to zap_pid_ns_processes > we get the guarantee that pid == 1 in a pid namespace will be the last > task that release_task is called on. > > With pid == 1 being the last task to pass through release_task > pid_ns_release_proc can no longer be called too early nor can wait > return before all of the EXIT_DEAD tasks in a pid namespace have exited. > > Signed-off-by: Eric W. Biederman > Signed-off-by: Oleg Nesterov Acked-by: Pavel Emelyanov -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/