Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754027AbaDQSF5 (ORCPT ); Thu, 17 Apr 2014 14:05:57 -0400 Received: from mail-lb0-f175.google.com ([209.85.217.175]:59486 "EHLO mail-lb0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753778AbaDQSF2 (ORCPT ); Thu, 17 Apr 2014 14:05:28 -0400 MIME-Version: 1.0 In-Reply-To: <1397756821.2628.69.camel@willson.li.ssimo.org> References: <20140416180642.GG31074@redhat.com> <20140416185936.GJ31074@redhat.com> <534FF61B.4010901@redhat.com> <1397750674.2628.44.camel@willson.li.ssimo.org> <1397751853.2628.50.camel@willson.li.ssimo.org> <1397753323.2628.60.camel@willson.li.ssimo.org> <20140417171256.GB25334@redhat.com> <1397756025.2628.64.camel@willson.li.ssimo.org> <1397756821.2628.69.camel@willson.li.ssimo.org> From: Andy Lutomirski Date: Thu, 17 Apr 2014 11:05:01 -0700 Message-ID: Subject: Re: [PATCH 2/2] net: Implement SO_PASSCGROUP to enable passing cgroup path To: Simo Sorce Cc: Vivek Goyal , Daniel J Walsh , David Miller , Tejun Heo , "linux-kernel@vger.kernel.org" , lpoetter@redhat.com, cgroups@vger.kernel.org, kay@redhat.com, Network Development 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 Thu, Apr 17, 2014 at 10:47 AM, Simo Sorce wrote: > On Thu, 2014-04-17 at 10:35 -0700, Andy Lutomirski wrote: >> On Thu, Apr 17, 2014 at 10:33 AM, Simo Sorce wrote: >> > On Thu, 2014-04-17 at 10:26 -0700, Andy Lutomirski wrote: >> >> >> >> Not really. write(2) can't send SCM_CGROUP. Callers of sendmsg(2) >> >> who supply SCM_CGROUP are explicitly indicating that they want their >> >> cgroup associated with that message. Callers of write(2) and send(2) >> >> are simply indicating that they have some bytes that they want to >> >> shove into whatever's at the other end of the fd. >> > >> > But there is no attack vector that passes by tricking setuid binaries to >> > write to pre-opened file descriptors on sendmsg(), and for the other >> > cases (connected socket) journald can always cross check with >> > SO_PEERCGROUP, so why do we care again ? >> >> Because the proposed code does not do what I described, at least as >> far I as I can tell. > > You do realize that we have been speaking in hypothetical for a while > now ? > > Even without doing the SO_PEERCRED, you are not going to fool the log, > as it gathers a ton of other info about the process, and cgroup is just > one of the infos used to classify the log. > > There are also credentials, pid, and a lot of other things. > Even if a setuid binary could be tricked to send a message with an > "impostor" cgroup don't you think you'd see other things out of place ? > (wrong uid, wrong pid, etc...). Credentials and pid have much the same problem because SCM_CREDENTIALS is screwed up. That's not an excuse to screw up SCM_CGROUP in the same way. --Andy -- 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/