From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754150AbbCaNM4 (ORCPT ); Tue, 31 Mar 2015 09:12:56 -0400 Received: from mail-lb0-f174.google.com ([209.85.217.174]:35473 "EHLO mail-lb0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753517AbbCaNMv (ORCPT ); Tue, 31 Mar 2015 09:12:51 -0400 MIME-Version: 1.0 In-Reply-To: <1427807248.2117.117.camel@HansenPartnership.com> References: <1427447013.2250.9.camel@HansenPartnership.com> <1427788642.4411.12.camel@redhat.com> <1427807248.2117.117.camel@HansenPartnership.com> From: Andy Lutomirski Date: Tue, 31 Mar 2015 06:12:29 -0700 Message-ID: Subject: Re: [PATCH] devpts: Add ptmx_uid and ptmx_gid options To: James Bottomley Cc: Alexander Larsson , gnome-os-list@gnome.org, Linux Containers , "linux-kernel@vger.kernel.org" , mclasen@redhat.com, "Eric W. Biederman" , Linux FS Devel Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 31, 2015 at 6:07 AM, James Bottomley wrote: > On Tue, 2015-03-31 at 09:57 +0200, Alexander Larsson wrote: >> On fre, 2015-03-27 at 10:03 +0100, James Bottomley >> > >> > > On Fri, Feb 20, 2015 at 5:04 PM, Andy Lutomirski wrote: >> > > > It's currently impossible to mount devpts in a user namespace that >> > > > has no root user, since ptmx can't be created. >> > >> > This is where I stopped reading because it's not true ... because it is >> > possible, you just do it from the host as real root. >> >> The point is being able to set up a container as a user, not requiring >> the setup to be run as root at all. In my case container is a desktop >> application which will be started by the user, and will run as the user. >> There is no root involved in the call chain at all. > > I don't really like that use case: Most container setups are under the > control of an orchestration system (like LXC, OpenVZ or even Docker). > You typically get the orchestration system to do the dangerous > operations (mount being one of the bigger dangers) because it has the > capacity to vet them. I can see the value in allowing a user to set up > a container without an oversight system, but at the same time you're > increasing the security vulnerability of the system. Security is often > a result of policy, so now this embeds policy into the kernel. I > strongly feel we should define the list of things we expect an > unsupervised (as in with no orchestration system) container to do and > then revisit this once we've given it some thought. Try thinking "sandbox", not "container". The ability to create sandboxes without some root-installed orchestration is incredibly valuable. In any event, this ship sailed quite awhile ago. devpts is one of the smallish number of important missing features. --Andy