From mboxrd@z Thu Jan 1 00:00:00 1970 From: Colin Walters Subject: Re: [PATCH v3 4/4] Allow unprivileged chroot when safe Date: Mon, 30 Jan 2012 17:41:47 -0500 Message-ID: <1327963309.5355.7.camel@lenny> References: <0e2f0f54e19bff53a3739ecfddb4ffa9a6dbde4d.1327858005.git.luto@amacapital.net> <1327960736.5355.5.camel@lenny> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Will Drewry , linux-kernel@vger.kernel.org, Casey Schaufler , Linus Torvalds , Jamie Lokier , keescook@chromium.org, john.johansen@canonical.com, serge.hallyn@canonical.com, coreyb@linux.vnet.ibm.com, pmoore@redhat.com, eparis@redhat.com, djm@mindrot.org, segoon@openwall.com, rostedt@goodmis.org, jmorris@namei.org, scarybeasts@gmail.com, avi@redhat.com, penberg@cs.helsinki.fi, viro@zeniv.linux.org.uk, mingo@elte.hu, akpm@linux-foundation.org, khilman@ti.com, borislav.petkov@amd.com, amwang@redhat.com, oleg@redhat.com, ak@linux.intel.com, eric.dumazet@gmail.com, gregkh@suse.de, dhowells@redhat.com, daniel.lezcano@free.fr, linux-fsdevel@vger.kernel.org, linux-security-module@vger.kernel.org, olofj@chromium.org, mhalcrow@google.com, dlaor@redhat.com, corbet@lwn.net, alan@lxorguk. To: Andy Lutomirski Return-path: In-Reply-To: Sender: linux-security-module-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Mon, 2012-01-30 at 14:10 -0800, Andy Lutomirski wrote: > On Mon, Jan 30, 2012 at 1:58 PM, Colin Walters wrote: > > On Mon, 2012-01-30 at 08:17 -0800, Andy Lutomirski wrote: > >> Chroot can easily be used to subvert setuid programs. If no_new_privs, > >> then setuid programs don't gain any privilege, so allow chroot. > > > > Is this needed/desired by anyone now, or are you just using it to "demo" > > NO_NEW_PRIVS? I don't see it as very useful on its own, since in any > > "container"-type chroot you really want /proc and /dev, and your patch > > doesn't help with that. > > It's a demo, but it could still be useful for container-ish things. > If something privileged sets up /proc, /sys, and /dev, then > unprivileged code can chroot into the container. This would allow > much simpler implementations of tools like schroot. What's the win if you still need a setuid binary? schroot (and my linux-user chroot binary) can just as easily call chroot as they can create bind mounts; I'm not buying a code complexity argument. > With this change, they wouldn't need to start privileged. > (Admittedly, this isn't a great argument for this patch.) Right...I'm not aware of anyone who would find that useful.