From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2D312C4363A for ; Fri, 30 Oct 2020 02:18:14 +0000 (UTC) Received: from fraxinus.osuosl.org (smtp4.osuosl.org [140.211.166.137]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 698EA20756 for ; Fri, 30 Oct 2020 02:18:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 698EA20756 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=hallyn.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=containers-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by fraxinus.osuosl.org (Postfix) with ESMTP id C0B6186AE9; Fri, 30 Oct 2020 02:18:12 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from fraxinus.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id StLTqMadHzDg; Fri, 30 Oct 2020 02:18:11 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by fraxinus.osuosl.org (Postfix) with ESMTP id AEA7086AE0; Fri, 30 Oct 2020 02:18:11 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 92412C0859; Fri, 30 Oct 2020 02:18:11 +0000 (UTC) Received: from whitealder.osuosl.org (smtp1.osuosl.org [140.211.166.138]) by lists.linuxfoundation.org (Postfix) with ESMTP id 862D8C0051 for ; Fri, 30 Oct 2020 02:18:10 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by whitealder.osuosl.org (Postfix) with ESMTP id 6B3DC869C4 for ; Fri, 30 Oct 2020 02:18:10 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from whitealder.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id XyhMptLQVSzf for ; Fri, 30 Oct 2020 02:18:09 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from mail.hallyn.com (mail.hallyn.com [178.63.66.53]) by whitealder.osuosl.org (Postfix) with ESMTPS id C708686990 for ; Fri, 30 Oct 2020 02:18:08 +0000 (UTC) Received: by mail.hallyn.com (Postfix, from userid 1001) id 027D69B4; Thu, 29 Oct 2020 21:18:05 -0500 (CDT) Date: Thu, 29 Oct 2020 21:18:05 -0500 From: "Serge E. Hallyn" To: "Eric W. Biederman" Subject: Re: [PATCH 00/34] fs: idmapped mounts Message-ID: <20201030021805.GA20489@mail.hallyn.com> References: <20201029003252.2128653-1-christian.brauner@ubuntu.com> <87pn51ghju.fsf@x220.int.ebiederm.org> <20201029155148.5odu4j2kt62ahcxq@yavin.dot.cyphar.com> <87361xdm4c.fsf@x220.int.ebiederm.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <87361xdm4c.fsf@x220.int.ebiederm.org> User-Agent: Mutt/1.9.4 (2018-02-28) Cc: Lennart Poettering , Mimi Zohar , David Howells , Andreas Dilger , containers@lists.linux-foundation.org, Tycho Andersen , Miklos Szeredi , smbarber@chromium.org, Christoph Hellwig , linux-ext4@vger.kernel.org, Mrunal Patel , Kees Cook , Arnd Bergmann , Jann Horn , selinux@vger.kernel.org, Josh Triplett , linux-fsdevel@vger.kernel.org, Alexander Viro , Andy Lutomirski , OGAWA Hirofumi , Geoffrey Thomas , James Bottomley , John Johansen , Theodore Tso , Seth Forshee , Dmitry Kasatkin , Stephen Smalley , Jonathan Corbet , linux-unionfs@vger.kernel.org, linux-security-module@vger.kernel.org, linux-audit@redhat.com, linux-api@vger.kernel.org, Casey Schaufler , Alban Crequy , linux-integrity@vger.kernel.org, Todd Kjos X-BeenThere: containers@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux Containers List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: containers-bounces@lists.linux-foundation.org Sender: "Containers" On Thu, Oct 29, 2020 at 11:37:23AM -0500, Eric W. Biederman wrote: > Aleksa Sarai writes: > > > On 2020-10-29, Eric W. Biederman wrote: > >> Christian Brauner writes: > >> > >> > Hey everyone, > >> > > >> > I vanished for a little while to focus on this work here so sorry for > >> > not being available by mail for a while. > >> > > >> > Since quite a long time we have issues with sharing mounts between > >> > multiple unprivileged containers with different id mappings, sharing a > >> > rootfs between multiple containers with different id mappings, and also > >> > sharing regular directories and filesystems between users with different > >> > uids and gids. The latter use-cases have become even more important with > >> > the availability and adoption of systemd-homed (cf. [1]) to implement > >> > portable home directories. > >> > >> Can you walk us through the motivating use case? > >> > >> As of this year's LPC I had the distinct impression that the primary use > >> case for such a feature was due to the RLIMIT_NPROC problem where two > >> containers with the same users still wanted different uid mappings to > >> the disk because the users were conflicting with each other because of > >> the per user rlimits. > >> > >> Fixing rlimits is straight forward to implement, and easier to manage > >> for implementations and administrators. > > > > This is separate to the question of "isolated user namespaces" and > > managing different mappings between containers. This patchset is solving > > the same problem that shiftfs solved -- sharing a single directory tree > > between containers that have different ID mappings. rlimits (nor any of > > the other proposals we discussed at LPC) will help with this problem. > > First and foremost: A uid shift on write to a filesystem is a security > bug waiting to happen. This is especially in the context of facilities > like iouring, that play very agressive games with how process context > makes it to system calls. > > The only reason containers were not immediately exploitable when iouring > was introduced is because the mechanisms are built so that even if > something escapes containment the security properties still apply. > Changes to the uid when writing to the filesystem does not have that > property. The tiniest slip in containment will be a security issue. > > This is not even the least bit theoretical. I have seem reports of how > shitfs+overlayfs created a situation where anyone could read > /etc/shadow. > > If you are going to write using the same uid to disk from different > containers the question becomes why can't those containers configure > those users to use the same kuid? Because if user 'myapp' in two otherwise isolated containers both have the same kuid, so that they can write to a shared directory, then root in container 1 has privilege over all files owned by 'myapp' in container 2. Whereas if they can each have distinct kuids, but when writing to the shared fs have a shared uid not otherwise belonging to either container, their rootfs's can remain completely off limits to each other. > What fixing rlimits does is it fixes one of the reasons that different > containers could not share the same kuid for users that want to write to > disk with the same uid. > > > I humbly suggest that it will be more secure, and easier to maintain for > both developers and users if we fix the reasons people want different > containers to have the same user running with different kuids. > > If not what are the reasons we fundamentally need the same on-disk user > using multiple kuids in the kernel? > > Eric _______________________________________________ Containers mailing list Containers@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/containers From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3887FC2D0A3 for ; Fri, 30 Oct 2020 02:18:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D80582076B for ; Fri, 30 Oct 2020 02:18:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725926AbgJ3CSJ (ORCPT ); Thu, 29 Oct 2020 22:18:09 -0400 Received: from mail.hallyn.com ([178.63.66.53]:38118 "EHLO mail.hallyn.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725781AbgJ3CSJ (ORCPT ); Thu, 29 Oct 2020 22:18:09 -0400 Received: by mail.hallyn.com (Postfix, from userid 1001) id 027D69B4; Thu, 29 Oct 2020 21:18:05 -0500 (CDT) Date: Thu, 29 Oct 2020 21:18:05 -0500 From: "Serge E. Hallyn" To: "Eric W. Biederman" Cc: Aleksa Sarai , Christian Brauner , Alexander Viro , Christoph Hellwig , linux-fsdevel@vger.kernel.org, John Johansen , James Morris , Mimi Zohar , Dmitry Kasatkin , Stephen Smalley , Casey Schaufler , Arnd Bergmann , Andreas Dilger , OGAWA Hirofumi , Geoffrey Thomas , Mrunal Patel , Josh Triplett , Andy Lutomirski , Amir Goldstein , Miklos Szeredi , Theodore Tso , Alban Crequy , Tycho Andersen , David Howells , James Bottomley , Jann Horn , Seth Forshee , =?iso-8859-1?Q?St=E9phane?= Graber , Lennart Poettering , smbarber@chromium.org, Phil Estes , Serge Hallyn , Kees Cook , Todd Kjos , Jonathan Corbet , containers@lists.linux-foundation.org, linux-security-module@vger.kernel.org, linux-api@vger.kernel.org, linux-ext4@vger.kernel.org, linux-unionfs@vger.kernel.org, linux-audit@redhat.com, linux-integrity@vger.kernel.org, selinux@vger.kernel.org Subject: Re: [PATCH 00/34] fs: idmapped mounts Message-ID: <20201030021805.GA20489@mail.hallyn.com> References: <20201029003252.2128653-1-christian.brauner@ubuntu.com> <87pn51ghju.fsf@x220.int.ebiederm.org> <20201029155148.5odu4j2kt62ahcxq@yavin.dot.cyphar.com> <87361xdm4c.fsf@x220.int.ebiederm.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87361xdm4c.fsf@x220.int.ebiederm.org> User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-unionfs@vger.kernel.org On Thu, Oct 29, 2020 at 11:37:23AM -0500, Eric W. Biederman wrote: > Aleksa Sarai writes: > > > On 2020-10-29, Eric W. Biederman wrote: > >> Christian Brauner writes: > >> > >> > Hey everyone, > >> > > >> > I vanished for a little while to focus on this work here so sorry for > >> > not being available by mail for a while. > >> > > >> > Since quite a long time we have issues with sharing mounts between > >> > multiple unprivileged containers with different id mappings, sharing a > >> > rootfs between multiple containers with different id mappings, and also > >> > sharing regular directories and filesystems between users with different > >> > uids and gids. The latter use-cases have become even more important with > >> > the availability and adoption of systemd-homed (cf. [1]) to implement > >> > portable home directories. > >> > >> Can you walk us through the motivating use case? > >> > >> As of this year's LPC I had the distinct impression that the primary use > >> case for such a feature was due to the RLIMIT_NPROC problem where two > >> containers with the same users still wanted different uid mappings to > >> the disk because the users were conflicting with each other because of > >> the per user rlimits. > >> > >> Fixing rlimits is straight forward to implement, and easier to manage > >> for implementations and administrators. > > > > This is separate to the question of "isolated user namespaces" and > > managing different mappings between containers. This patchset is solving > > the same problem that shiftfs solved -- sharing a single directory tree > > between containers that have different ID mappings. rlimits (nor any of > > the other proposals we discussed at LPC) will help with this problem. > > First and foremost: A uid shift on write to a filesystem is a security > bug waiting to happen. This is especially in the context of facilities > like iouring, that play very agressive games with how process context > makes it to system calls. > > The only reason containers were not immediately exploitable when iouring > was introduced is because the mechanisms are built so that even if > something escapes containment the security properties still apply. > Changes to the uid when writing to the filesystem does not have that > property. The tiniest slip in containment will be a security issue. > > This is not even the least bit theoretical. I have seem reports of how > shitfs+overlayfs created a situation where anyone could read > /etc/shadow. > > If you are going to write using the same uid to disk from different > containers the question becomes why can't those containers configure > those users to use the same kuid? Because if user 'myapp' in two otherwise isolated containers both have the same kuid, so that they can write to a shared directory, then root in container 1 has privilege over all files owned by 'myapp' in container 2. Whereas if they can each have distinct kuids, but when writing to the shared fs have a shared uid not otherwise belonging to either container, their rootfs's can remain completely off limits to each other. > What fixing rlimits does is it fixes one of the reasons that different > containers could not share the same kuid for users that want to write to > disk with the same uid. > > > I humbly suggest that it will be more secure, and easier to maintain for > both developers and users if we fix the reasons people want different > containers to have the same user running with different kuids. > > If not what are the reasons we fundamentally need the same on-disk user > using multiple kuids in the kernel? > > Eric From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E90A5C4363A for ; Fri, 30 Oct 2020 02:25:07 +0000 (UTC) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [63.128.21.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0EDAB20756 for ; Fri, 30 Oct 2020 02:25:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0EDAB20756 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=hallyn.com Authentication-Results: mail.kernel.org; spf=tempfail smtp.mailfrom=linux-audit-bounces@redhat.com Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-180-dec57zBCOS6f82_b29so8Q-1; Thu, 29 Oct 2020 22:25:03 -0400 X-MC-Unique: dec57zBCOS6f82_b29so8Q-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8BACB425CB; Fri, 30 Oct 2020 02:25:00 +0000 (UTC) Received: from colo-mx.corp.redhat.com (colo-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.20]) by smtp.corp.redhat.com (Postfix) with ESMTPS id BF72C6115F; Fri, 30 Oct 2020 02:24:58 +0000 (UTC) Received: from lists01.pubmisc.prod.ext.phx2.redhat.com (lists01.pubmisc.prod.ext.phx2.redhat.com [10.5.19.33]) by colo-mx.corp.redhat.com (Postfix) with ESMTP id B2B3D181A06C; Fri, 30 Oct 2020 02:24:54 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) by lists01.pubmisc.prod.ext.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id 09U2IJ76008145 for ; Thu, 29 Oct 2020 22:18:19 -0400 Received: by smtp.corp.redhat.com (Postfix) id 1949E2156A49; Fri, 30 Oct 2020 02:18:19 +0000 (UTC) Received: from mimecast-mx02.redhat.com (mimecast01.extmail.prod.ext.rdu2.redhat.com [10.11.55.17]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 13C932157F4F for ; Fri, 30 Oct 2020 02:18:13 +0000 (UTC) Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [207.211.31.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id DF2FB858298 for ; Fri, 30 Oct 2020 02:18:12 +0000 (UTC) Received: from mail.hallyn.com (mail.hallyn.com [178.63.66.53]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-445-LIxZr0yNNVmFA92tx6neeQ-1; Thu, 29 Oct 2020 22:18:08 -0400 X-MC-Unique: LIxZr0yNNVmFA92tx6neeQ-1 Received: by mail.hallyn.com (Postfix, from userid 1001) id 027D69B4; Thu, 29 Oct 2020 21:18:05 -0500 (CDT) Date: Thu, 29 Oct 2020 21:18:05 -0500 From: "Serge E. Hallyn" To: "Eric W. Biederman" Subject: Re: [PATCH 00/34] fs: idmapped mounts Message-ID: <20201030021805.GA20489@mail.hallyn.com> References: <20201029003252.2128653-1-christian.brauner@ubuntu.com> <87pn51ghju.fsf@x220.int.ebiederm.org> <20201029155148.5odu4j2kt62ahcxq@yavin.dot.cyphar.com> <87361xdm4c.fsf@x220.int.ebiederm.org> MIME-Version: 1.0 In-Reply-To: <87361xdm4c.fsf@x220.int.ebiederm.org> User-Agent: Mutt/1.9.4 (2018-02-28) X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-loop: linux-audit@redhat.com X-Mailman-Approved-At: Thu, 29 Oct 2020 22:24:47 -0400 Cc: Phil Estes , Lennart Poettering , Amir Goldstein , Mimi Zohar , David Howells , Andreas Dilger , containers@lists.linux-foundation.org, Christian Brauner , Tycho Andersen , Miklos Szeredi , James Morris , smbarber@chromium.org, Christoph Hellwig , linux-ext4@vger.kernel.org, Mrunal Patel , Serge Hallyn , Arnd Bergmann , Jann Horn , selinux@vger.kernel.org, Josh Triplett , linux-fsdevel@vger.kernel.org, Aleksa Sarai , Alexander Viro , Andy Lutomirski , OGAWA Hirofumi , Geoffrey Thomas , James Bottomley , John Johansen , Theodore Tso , Seth Forshee , Dmitry Kasatkin , Jonathan Corbet , linux-unionfs@vger.kernel.org, linux-security-module@vger.kernel.org, linux-audit@redhat.com, linux-api@vger.kernel.org, Alban Crequy , linux-integrity@vger.kernel.org, =?iso-8859-1?Q?St=E9phane?= Graber , Todd Kjos X-BeenThere: linux-audit@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: Linux Audit Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-audit-bounces@redhat.com Errors-To: linux-audit-bounces@redhat.com X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=linux-audit-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On Thu, Oct 29, 2020 at 11:37:23AM -0500, Eric W. Biederman wrote: > Aleksa Sarai writes: > > > On 2020-10-29, Eric W. Biederman wrote: > >> Christian Brauner writes: > >> > >> > Hey everyone, > >> > > >> > I vanished for a little while to focus on this work here so sorry for > >> > not being available by mail for a while. > >> > > >> > Since quite a long time we have issues with sharing mounts between > >> > multiple unprivileged containers with different id mappings, sharing a > >> > rootfs between multiple containers with different id mappings, and also > >> > sharing regular directories and filesystems between users with different > >> > uids and gids. The latter use-cases have become even more important with > >> > the availability and adoption of systemd-homed (cf. [1]) to implement > >> > portable home directories. > >> > >> Can you walk us through the motivating use case? > >> > >> As of this year's LPC I had the distinct impression that the primary use > >> case for such a feature was due to the RLIMIT_NPROC problem where two > >> containers with the same users still wanted different uid mappings to > >> the disk because the users were conflicting with each other because of > >> the per user rlimits. > >> > >> Fixing rlimits is straight forward to implement, and easier to manage > >> for implementations and administrators. > > > > This is separate to the question of "isolated user namespaces" and > > managing different mappings between containers. This patchset is solving > > the same problem that shiftfs solved -- sharing a single directory tree > > between containers that have different ID mappings. rlimits (nor any of > > the other proposals we discussed at LPC) will help with this problem. > > First and foremost: A uid shift on write to a filesystem is a security > bug waiting to happen. This is especially in the context of facilities > like iouring, that play very agressive games with how process context > makes it to system calls. > > The only reason containers were not immediately exploitable when iouring > was introduced is because the mechanisms are built so that even if > something escapes containment the security properties still apply. > Changes to the uid when writing to the filesystem does not have that > property. The tiniest slip in containment will be a security issue. > > This is not even the least bit theoretical. I have seem reports of how > shitfs+overlayfs created a situation where anyone could read > /etc/shadow. > > If you are going to write using the same uid to disk from different > containers the question becomes why can't those containers configure > those users to use the same kuid? Because if user 'myapp' in two otherwise isolated containers both have the same kuid, so that they can write to a shared directory, then root in container 1 has privilege over all files owned by 'myapp' in container 2. Whereas if they can each have distinct kuids, but when writing to the shared fs have a shared uid not otherwise belonging to either container, their rootfs's can remain completely off limits to each other. > What fixing rlimits does is it fixes one of the reasons that different > containers could not share the same kuid for users that want to write to > disk with the same uid. > > > I humbly suggest that it will be more secure, and easier to maintain for > both developers and users if we fix the reasons people want different > containers to have the same user running with different kuids. > > If not what are the reasons we fundamentally need the same on-disk user > using multiple kuids in the kernel? > > Eric -- Linux-audit mailing list Linux-audit@redhat.com https://www.redhat.com/mailman/listinfo/linux-audit