Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755487AbaKSKiS (ORCPT ); Wed, 19 Nov 2014 05:38:18 -0500 Received: from mail-qc0-f182.google.com ([209.85.216.182]:54399 "EHLO mail-qc0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753708AbaKSKiP (ORCPT ); Wed, 19 Nov 2014 05:38:15 -0500 MIME-Version: 1.0 X-Originating-IP: [46.139.80.5] In-Reply-To: References: <1414013060-137148-1-git-send-email-seth.forshee@canonical.com> <1414013060-137148-3-git-send-email-seth.forshee@canonical.com> <20141111140454.GD333@tucsk> <87mw7xd9zt.fsf@x220.int.ebiederm.org> <20141112130915.GG333@tucsk> <20141112162254.GB31775@ubuntu-hedt> <20141118152156.GA21726@ubuntu-mba51> Date: Wed, 19 Nov 2014 11:38:14 +0100 Message-ID: Subject: Re: [PATCH v5 2/4] fuse: Support fuse filesystems outside of init_user_ns From: Miklos Szeredi To: Seth Forshee Cc: "Eric W. Biederman" , "Serge H. Hallyn" , Andy Lutomirski , Michael j Theall , fuse-devel , Kernel Mailing List , Linux-Fsdevel 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 Wed, Nov 19, 2014 at 9:50 AM, Miklos Szeredi wrote: > On Tue, Nov 18, 2014 at 4:21 PM, Seth Forshee > wrote: >>> I asked around a bit, and it turns out there are use cases for nested >> containers (i.e. a container within a container) where the rootfs for >> the outer container mounts a filesystem containing the rootfs for the >> inner container. If that mount is nosuid then suid utilities like ping >> aren't going to work in the inner container. >> >> So since there's a use case for suid in a userns mount and we have what >> we belive are sufficient protections against using this as a vector to >> get privileges outside the container, I'm planning to move ahead without >> the MNT_NOSUID restriction. Any objections? > > In the general case how'd we prevent suid executable being tricked to > do something it shouldn't do by unprivileged mounting into sensitive > places (i.e. config files) inside the container? > > Allowing SUID looks like a slippery slope to me. And there are plenty > of solutions to the "ping" problem, AFAICS, that don't involve the > suid bit. ping isn't even suid on my system, it has security.capability xattr instead. Please just get rid of SUID/SGID. It's a legacy, it's a hack, not worth the complexity and potential problems arising from that complexity. Thanks, Miklos -- 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/