From mboxrd@z Thu Jan 1 00:00:00 1970 From: ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org (Eric W. Biederman) Subject: Re: [PATCH] userns: allow privileged user to operate locked mount Date: Thu, 14 Nov 2013 17:38:48 -0800 Message-ID: <871u2i30lz.fsf@xmission.com> References: <1384327663-12032-1-git-send-email-gaofeng@cn.fujitsu.com> <874n7e4k78.fsf@xmission.com> <52856F0D.8090206@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <52856F0D.8090206-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org> (Gao feng's message of "Fri, 15 Nov 2013 08:47:09 +0800") List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Gao feng Cc: linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: containers.vger.kernel.org Gao feng writes: > On 11/15/2013 07:50 AM, Eric W. Biederman wrote: >> Gao feng writes: >> >>> Privileged user should have rights to mount/umount/move >>> these even locked mount. >> >> Hmm. This is pretty much a can't happen case, as the only exist in mount >> namespaces where the global root isn't the root. How are you getting >> into this situation? Using setns() ? >> > > Before, priviged user can use setns to set his mount namespace to the > container's mount namespace, and change container's mount directly. > this patch just gives back host the control of container. Having thought about this patch a little more I really don't like it. There are other ways for a privileged user to get around the limitations when the mount namespace is being created or the mounts are being propagated. This approach would require more then a signgle bit of accounting to work in the nested user namespace case. The lock says one or several mounts are mounted as a unit and need to stay that way. If there are real advantages to splitting things up I might be persuaded to change my mind. But right now it looks like you are introducing extra complexity for a very corner edge case that we don't want to encourage people to use. Eric From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755871Ab3KOBjG (ORCPT ); Thu, 14 Nov 2013 20:39:06 -0500 Received: from out03.mta.xmission.com ([166.70.13.233]:41966 "EHLO out03.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754735Ab3KOBi5 (ORCPT ); Thu, 14 Nov 2013 20:38:57 -0500 From: ebiederm@xmission.com (Eric W. Biederman) To: Gao feng Cc: containers@lists.linux-foundation.org, linux-fsdevel@vger.kernel.org, serge@hallyn.com, linux-kernel@vger.kernel.org References: <1384327663-12032-1-git-send-email-gaofeng@cn.fujitsu.com> <874n7e4k78.fsf@xmission.com> <52856F0D.8090206@cn.fujitsu.com> Date: Thu, 14 Nov 2013 17:38:48 -0800 In-Reply-To: <52856F0D.8090206@cn.fujitsu.com> (Gao feng's message of "Fri, 15 Nov 2013 08:47:09 +0800") Message-ID: <871u2i30lz.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/urIirb5Op7uHvYGMBTmJZ2TRWAkiVDSU= 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 * 0.7 XMSubLong Long Subject * 0.0 T_TM2_M_HEADER_IN_MSG BODY: T_TM2_M_HEADER_IN_MSG * -3.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% * [score: 0.0013] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa06 1397; Body=1 Fuz1=1 Fuz2=1] X-Spam-DCC: XMission; sa06 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Gao feng X-Spam-Relay-Country: Subject: Re: [PATCH] userns: allow privileged user to operate locked mount 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 in01.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Gao feng writes: > On 11/15/2013 07:50 AM, Eric W. Biederman wrote: >> Gao feng writes: >> >>> Privileged user should have rights to mount/umount/move >>> these even locked mount. >> >> Hmm. This is pretty much a can't happen case, as the only exist in mount >> namespaces where the global root isn't the root. How are you getting >> into this situation? Using setns() ? >> > > Before, priviged user can use setns to set his mount namespace to the > container's mount namespace, and change container's mount directly. > this patch just gives back host the control of container. Having thought about this patch a little more I really don't like it. There are other ways for a privileged user to get around the limitations when the mount namespace is being created or the mounts are being propagated. This approach would require more then a signgle bit of accounting to work in the nested user namespace case. The lock says one or several mounts are mounted as a unit and need to stay that way. If there are real advantages to splitting things up I might be persuaded to change my mind. But right now it looks like you are introducing extra complexity for a very corner edge case that we don't want to encourage people to use. Eric