From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757042AbZDOVQp (ORCPT ); Wed, 15 Apr 2009 17:16:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752853AbZDOVQf (ORCPT ); Wed, 15 Apr 2009 17:16:35 -0400 Received: from e38.co.us.ibm.com ([32.97.110.159]:41608 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752524AbZDOVQf (ORCPT ); Wed, 15 Apr 2009 17:16:35 -0400 Date: Wed, 15 Apr 2009 16:16:09 -0500 From: "Serge E. Hallyn" To: Oren Laadan Cc: Dave Hansen , xemul@parallels.com, containers@lists.linux-foundation.org, mingo@elte.hu, linux-kernel@vger.kernel.org, hch@infradead.org, akpm@linux-foundation.org, torvalds@linux-foundation.org, Alexey Dobriyan Subject: Re: CAP_SYS_ADMIN on restart(2) Message-ID: <20090415211609.GA6704@us.ibm.com> References: <20090413091423.GA19236@x200.localdomain> <49E4108A.8050201@cs.columbia.edu> <20090414145830.GA27461@x200.localdomain> <49E4D115.5080601@cs.columbia.edu> <20090414204912.GA28458@x200.localdomain> <20090414213934.GB17986@us.ibm.com> <20090415192150.GC26994@x200.localdomain> <1239827033.32604.167.camel@nimitz> <20090415203920.GA5475@us.ibm.com> <49E64BFF.5080002@cs.columbia.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <49E64BFF.5080002@cs.columbia.edu> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Quoting Oren Laadan (orenl@cs.columbia.edu): > > > Serge E. Hallyn wrote: > > Quoting Dave Hansen (dave@linux.vnet.ibm.com): > >> On Wed, 2009-04-15 at 23:21 +0400, Alexey Dobriyan wrote: > >>> Is sysctl to control CAP_SYS_ADMIN on restart(2) OK? > >> If the point is not to let users even *try* restarting things if it > >> *might* not work, then I guess this might be reasonable. > >> > >> If the goal is to increase security by always requiring CAP_SYS_ADMIN > >> for "dangerous" operations, I fear it will be harmful. We may have > >> people adding features that are not considering the security impact of > >> what they're doing just because the cases they care about all require > >> privilege. > > > > Nah, I disagree. (Or put another way, that wouldn't be the goal) > > There are two administrators we want to satisfy: > > > > 1. the one who wants his users to do partial checkpoints, but doesn't > > want to risk giving away any privilege at all in the process. He'll > > be satisified by setting restart(2) to not require cap_sys_admin, > > and his users just won't be able to do a whole container. A lot of > > users will be happy with that (though no SYSVIPC support, then). > > There is also a middle way: use setuid program to allow creation > of a new namespace (under your favorite policy), then drop the > privileges and continue as unprivileged inside that container. > > IOW, don't make the initial container-creation a barrier for the > entire operation. That is still possible here. But I don't think it's relevant. What Alexey wants, I believe, is for users to be able to not have to worry about there being exploitable bugs in restart(2) which unprivileged users can play with. And for the usual distro-kernel reasons, saying use 'CONFIG_CHECKPOINT=n' is not an option. -serge