From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755486Ab3IAEpY (ORCPT ); Sun, 1 Sep 2013 00:45:24 -0400 Received: from out03.mta.xmission.com ([166.70.13.233]:46652 "EHLO out03.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753369Ab3IAEpW (ORCPT ); Sun, 1 Sep 2013 00:45:22 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Andy Lutomirski Cc: Linux Containers , "Serge E. Hallyn" , Linux FS Devel , "linux-kernel\@vger.kernel.org" References: <878uzmhkqg.fsf@xmission.com> <87a9k2g5la.fsf@xmission.com> Date: Sat, 31 Aug 2013 21:45:11 -0700 In-Reply-To: <87a9k2g5la.fsf@xmission.com> (Eric W. Biederman's message of "Tue, 27 Aug 2013 14:57:05 -0700") Message-ID: <87eh99noa0.fsf@xmission.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-AID: U2FsdGVkX1/6KlSvpw3CdDV4dkvBWi+tosBv97DwCjk= X-SA-Exim-Connect-IP: 98.207.154.105 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 1.5 XMNoVowels Alpha-numberic number with no vowels * 1.5 TR_Symld_Words too many words that have symbols inside * 0.7 XMSubLong Long Subject * 0.0 T_TM2_M_HEADER_IN_MSG BODY: T_TM2_M_HEADER_IN_MSG * -0.5 BAYES_05 BODY: Bayes spam probability is 1 to 5% * [score: 0.0316] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa05 1397; Body=1 Fuz1=1 Fuz2=1] X-Spam-DCC: XMission; sa05 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: **;Andy Lutomirski X-Spam-Relay-Country: Subject: Re: [REVIEW][PATCH 1/2] userns: Better restrictions on when proc and sysfs can be mounted X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Wed, 14 Nov 2012 14:26:46 -0700) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ebiederm@xmission.com (Eric W. Biederman) writes: > Andy Lutomirski writes: > >> On Tue, Aug 27, 2013 at 2:44 PM, Eric W. Biederman >> wrote: >>> >>> Rely on the fact that another flavor of the filesystem is already >>> mounted and do not rely on state in the user namespace. >> >> Possibly dumb question: does this check whether the pre-existing mount >> has hidepid set? > > Not currently. > > It may be worth doing something with respect to hidepid. I forget what > hidepid tries to do, and I need to dash. But feel free to cook up a > follow on patch. So I have thought about this a bit more. hidepid hides the processes that ptrace_may_access will fail on. You can only reach the point where an unprivileged mount of a pid namespace is possible if you have created both a user namespace and a pid namespace. Which means the creator of the pid namespace will be capable of ptracing all of the other processes in the pid namespace (ignoring setns). So I don't see a point of worry about hidepid or the hidepid gid on child pid namespaces. The cases it is attempting to protecting against really don't exist. Eric