From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422640AbWGNRAS (ORCPT ); Fri, 14 Jul 2006 13:00:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161269AbWGNRAS (ORCPT ); Fri, 14 Jul 2006 13:00:18 -0400 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:42655 "EHLO ebiederm.dsl.xmission.com") by vger.kernel.org with ESMTP id S1161267AbWGNRAQ (ORCPT ); Fri, 14 Jul 2006 13:00:16 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: "Serge E. Hallyn" Cc: Cedric Le Goater , linux-kernel@vger.kernel.org, Andrew Morton , Kirill Korotaev , Andrey Savochkin , Herbert Poetzl , Sam Vilain , Dave Hansen Subject: Re: [PATCH -mm 5/7] add user namespace References: <20060711075051.382004000@localhost.localdomain> <20060711075420.937831000@localhost.localdomain> <44B50088.1010103@fr.ibm.com> <20060714141728.GE28436@sergelap.austin.ibm.com> <20060714164640.GC25303@sergelap.austin.ibm.com> Date: Fri, 14 Jul 2006 10:58:57 -0600 In-Reply-To: <20060714164640.GC25303@sergelap.austin.ibm.com> (Serge E. Hallyn's message of "Fri, 14 Jul 2006 11:46:40 -0500") Message-ID: User-Agent: Gnus/5.110004 (No Gnus v0.4) Emacs/21.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org "Serge E. Hallyn" writes: > Quoting Eric W. Biederman (ebiederm@xmission.com): >> "Serge E. Hallyn" writes: >> >> No. The uids in a filesystem are interpreted in some user namespace >> >> context. We can discover that context at the first mount of the >> >> filesystem. Assuming the uids on a filesystem are the same set >> >> of uids your process is using is just wrong. >> > >> > But, when I insert a usb keychain disk into my laptop, that fs assumes >> > the uids on it's fs are the same as uids on my laptop... >> >> I agree that setting the fs_user_namespace at mount time is fine. >> However when we use a mount that a process in another user namespace >> we need to not assume the uids are the same. >> >> Do you see the difference? > > Aaah - so you don't want to store this on the fs. So this is actually > like what I had mentioned many many emails ago? Quite possibly. I'm not certain where you go the idea I was thinking of storing this on the fs. I think you must have been thinking of the Linux-Vserver implementation. >> Actually I was thinking something as mundane as a mapping table. This >> uid in this namespace equals that uid in that other namespace. > > I see. > > That's also what I was imagining earlier, but it seems crass somehow. > I'd almost prefer to just tag a mount with a user namespace implicitly, > and only allow the mounter to say 'do' or 'don't' allow this to be read > by users in another namespace. Then in the 'don't' case, user joe > [1000] can't read files belonging to user jack [1000] in another > namespace. It's stricter, but clean. > > But whether we do mapping tables or simple isolation, I do still like > the idea of pursuing the use of the keystore for global uids. Yes. I guess my thinking is that the mapping effort and keys are an enhancement after we get the basic user namespace working, to overcome the limitations. Eric