From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764510AbYDCTqY (ORCPT ); Thu, 3 Apr 2008 15:46:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759203AbYDCToV (ORCPT ); Thu, 3 Apr 2008 15:44:21 -0400 Received: from e6.ny.us.ibm.com ([32.97.182.146]:35118 "EHLO e6.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762670AbYDCToU (ORCPT ); Thu, 3 Apr 2008 15:44:20 -0400 Date: Thu, 3 Apr 2008 14:44:18 -0500 From: "Serge E. Hallyn" To: "Eric W. Biederman" Cc: Pavel Emelyanov , Manfred Spraul , Linux Kernel Mailing List , Andrew Morton , Serge Hallyn , Sukadev Bhattiprolu Subject: Re: [RFC, PATCH] fix SEM_UNDO with namespaces Message-ID: <20080403194418.GA11105@sergelap.austin.ibm.com> References: <47EFFD1C.5020204@colorfullife.com> <47F08ED6.1090103@openvz.org> <47F10DF7.5010702@colorfullife.com> <47F203EC.7090806@openvz.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.16 (2007-06-09) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Quoting Eric W. Biederman (ebiederm@xmission.com): > Pavel Emelyanov writes: > >>> I agree, that we should probably destroy this one when the task calls > >>> unshare, but trying to keep this list relevant is useless. > >>> > >> A very tricky question: Let's assume we have a process with two threads. > >> The undo structure is shared, as per opengroup standard. > >> Now one thread calls unshare(CLONE_NEWIPC). What should happen? We > >> cannot destroy the undo structure, the other thread might be still > >> interested in it. > >> If we allow sys_unshare() for multithreaded processes with CLONE_NEWIPC > >> and without CLONE_SYSVSEM, then we must handle this case. > > > > Hm... I'd simply disable creating any new namespaces for threads. > > I think other namespaces developers agree with me. Serge, Suka, Eric > > what do you think? > > I almost agree. sys_unshare() in a multithreaded process breaks > all kinds of user space libs. So you can only reasonably look at > the problem as what we do with linux tasks that share some things > and not others. The posix/opengroup notion of processes and threads > are a distraction. > > In this case requiring it appears that to require unsharing both > CLONE_SYSVSEM and CLONE_NEWIPC at the same time. (i.e. unshare > of CLONE_SYSVSEM should fail if CLONE_NEWIPC is not also specified). > > Then to make it work we make unshare of SYSVSEM succeed when it is > not shared. > > This looks like about a 5 line patch or two. > > The effect is because we don't support unsharing of SYSVSEM currently > we don't support a threaded process unsharing the ipc namespace. > > Eric Eric, does the following patch correctly interpret your recommendation? Pavel does it make sense to you? thanks, -serge >>From 9c85fb3cb80cea1d888c3c253a9fb6e9bc173649 Mon Sep 17 00:00:00 2001 From: Serge E. Hallyn Date: Thu, 3 Apr 2008 12:43:23 -0700 Subject: [PATCH 1/1] ipc namespaces: fix svsem unsharing issue Refuse to unshare an ipcns if the semundo is shared and we are not requesting a new SYSVSEM Signed-off-by: Serge E. Hallyn --- ipc/namespace.c | 10 ++++++++++ 1 files changed, 10 insertions(+), 0 deletions(-) diff --git a/ipc/namespace.c b/ipc/namespace.c index 9171d94..9044505 100644 --- a/ipc/namespace.c +++ b/ipc/namespace.c @@ -48,6 +48,16 @@ struct ipc_namespace *copy_ipcs(unsigned long flags, struct ipc_namespace *ns) if (!(flags & CLONE_NEWIPC)) return ns; + if (!(flags & CLONE_SYSVSEM)) { + if (!current->sysvsem.undo_list) + goto ok; + if (atomic_read(¤t->sysvsem.undo_list->refcnt) == 1) + goto ok; + put_ipc_ns(ns); + return ERR_PTR(-EINVAL); + } + +ok: new_ns = clone_ipc_ns(ns); put_ipc_ns(ns); -- 1.5.3.6