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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 32253C433E9 for ; Fri, 29 Jan 2021 22:57:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CE64864E0C for ; Fri, 29 Jan 2021 22:57:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231132AbhA2W5l (ORCPT ); Fri, 29 Jan 2021 17:57:41 -0500 Received: from out01.mta.xmission.com ([166.70.13.231]:37276 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229683AbhA2W5j (ORCPT ); Fri, 29 Jan 2021 17:57:39 -0500 Received: from in02.mta.xmission.com ([166.70.13.52]) by out01.mta.xmission.com with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1l5ch8-00El2W-7c; Fri, 29 Jan 2021 15:56:50 -0700 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95] helo=x220.xmission.com) by in02.mta.xmission.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1l5ch7-002DyO-3c; Fri, 29 Jan 2021 15:56:49 -0700 From: ebiederm@xmission.com (Eric W. Biederman) To: "Serge E. Hallyn" Cc: Miklos Szeredi , linux-fsdevel@vger.kernel.org, linux-unionfs@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, Christian Brauner References: <20210119162204.2081137-1-mszeredi@redhat.com> <20210119162204.2081137-3-mszeredi@redhat.com> <8735yw8k7a.fsf@x220.int.ebiederm.org> <20210128165852.GA20974@mail.hallyn.com> <87o8h8x1a6.fsf@x220.int.ebiederm.org> <20210129154839.GC1130@mail.hallyn.com> Date: Fri, 29 Jan 2021 16:55:29 -0600 In-Reply-To: <20210129154839.GC1130@mail.hallyn.com> (Serge E. Hallyn's message of "Fri, 29 Jan 2021 09:48:39 -0600") Message-ID: <87im7fuzdq.fsf@x220.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1l5ch7-002DyO-3c;;;mid=<87im7fuzdq.fsf@x220.int.ebiederm.org>;;;hst=in02.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX19X3waKsp4zjyMN3J12N2O9HZ4lenytO+A= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH 2/2] security.capability: fix conversions on getxattr X-SA-Exim-Version: 4.2.1 (built Sat, 08 Feb 2020 21:53:50 +0000) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org "Serge E. Hallyn" writes: > On Thu, Jan 28, 2021 at 02:19:13PM -0600, Eric W. Biederman wrote: >> "Serge E. Hallyn" writes: >> >> > On Tue, Jan 19, 2021 at 07:34:49PM -0600, Eric W. Biederman wrote: >> >> Miklos Szeredi writes: >> >> >> >> > If a capability is stored on disk in v2 format cap_inode_getsecurity() will >> >> > currently return in v2 format unconditionally. >> >> > >> >> > This is wrong: v2 cap should be equivalent to a v3 cap with zero rootid, >> >> > and so the same conversions performed on it. >> >> > >> >> > If the rootid cannot be mapped v3 is returned unconverted. Fix this so >> >> > that both v2 and v3 return -EOVERFLOW if the rootid (or the owner of the fs >> >> > user namespace in case of v2) cannot be mapped in the current user >> >> > namespace. >> >> >> >> This looks like a good cleanup. >> > >> > Sorry, I'm not following. Why is this a good cleanup? Why should >> > the xattr be shown as faked v3 in this case? >> >> If the reader is in &init_user_ns. If the filesystem was mounted in a >> user namespace. Then the reader looses the information that the > > Can you be more precise about "filesystem was mounted in a user namespace"? > Is this a FUSE thing, the fs is marked as being mounted in a non-init userns? > If that's a possible case, then yes that must be represented as v3. Using > is_v2header() may be the simpler way to check for that, but the more accurate > check would be "is it v2 header and mounted by init_user_ns". I think the filesystems current relevant are fuse,overlayfs,ramfs,tmpfs. > Basically yes, in as many cases as possible we want to just give a v2 > cap because more userspace knows what to do with that, but a non-init-userns > mounted fs which provides a v2 fscap should have it represented as v3 cap > with rootid being the kuid that owns the userns. That is the case we that is being fixed in the patch. > Or am I still thinking wrongly? Wouldn't be entirely surprised :) No you got it. Eric