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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=unavailable 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 9EC76C43219 for ; Thu, 2 May 2019 03:57:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 63F522085A for ; Thu, 2 May 2019 03:57:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726189AbfEBD5Q (ORCPT ); Wed, 1 May 2019 23:57:16 -0400 Received: from mx2.suse.de ([195.135.220.15]:46684 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726186AbfEBD5Q (ORCPT ); Wed, 1 May 2019 23:57:16 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id A63C2AC10; Thu, 2 May 2019 03:57:13 +0000 (UTC) From: NeilBrown To: Amir Goldstein Date: Thu, 02 May 2019 13:57:03 +1000 Cc: "J. Bruce Fields" , Andreas Gruenbacher , Miklos Szeredi , Andreas =?utf-8?Q?Gr=C3=BCnbacher?= , Patrick Plagwitz , "linux-unionfs\@vger.kernel.org" , Linux NFS list , Linux FS-devel Mailing List , Linux Kernel Mailing List Subject: Re: [PATCH] overlayfs: ignore empty NFSv4 ACLs in ext4 upperdir In-Reply-To: References: <20161205151933.GA17517@fieldses.org> <20161205162559.GB17517@fieldses.org> <266c571f-e4e2-7c61-5ee2-8ece0c2d06e9@web.de> <20161206185806.GC31197@fieldses.org> <87bm0l4nra.fsf@notabene.neil.brown.name> Message-ID: <875zqt4igg.fsf@notabene.neil.brown.name> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha256; protocol="application/pgp-signature" Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org --=-=-= Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On Wed, May 01 2019, Amir Goldstein wrote: > On Wed, May 1, 2019 at 10:03 PM NeilBrown wrote: >> >> On Tue, Dec 06 2016, J. Bruce Fields wrote: >> >> > On Tue, Dec 06, 2016 at 02:18:31PM +0100, Andreas Gruenbacher wrote: >> >> On Tue, Dec 6, 2016 at 11:08 AM, Miklos Szeredi w= rote: >> >> > On Tue, Dec 6, 2016 at 12:24 AM, Andreas Gr=C3=BCnbacher >> >> > wrote: >> >> >> 2016-12-06 0:19 GMT+01:00 Andreas Gr=C3=BCnbacher : >> >> > >> >> >>> It's not hard to come up with a heuristic that determines if a >> >> >>> system.nfs4_acl value is equivalent to a file mode, and to ignore= the >> >> >>> attribute in that case. (The file mode is transmitted in its own >> >> >>> attribute already, so actually converting .) That way, overlayfs = could >> >> >>> still fail copying up files that have an actual ACL. It's still an >> >> >>> ugly hack ... >> >> >> >> >> >> Actually, that kind of heuristic would make sense in the NFS client >> >> >> which could then hide the "system.nfs4_acl" attribute. >> >> > >> >> > Even simpler would be if knfsd didn't send the attribute if not >> >> > necessary. Looks like there's code actively creating the nfs4_acl = on >> >> > the wire even if the filesystem had none: >> >> > >> >> > pacl =3D get_acl(inode, ACL_TYPE_ACCESS); >> >> > if (!pacl) >> >> > pacl =3D posix_acl_from_mode(inode->i_mode, GFP_KERNEL); >> >> > >> >> > What's the point? >> >> >> >> That's how the protocol is specified. >> > >> > Yep, even if we could make that change to nfsd it wouldn't help the >> > client with the large number of other servers that are out there >> > (including older knfsd's). >> > >> > --b. >> > >> >> (I'm not saying that that's very helpful.) >> >> >> >> Andreas >> >> Hi everyone..... >> I have a customer facing this problem, and so stumbled onto the email >> thread. >> Unfortunately it didn't resolve anything. Maybe I can help kick things >> along??? >> >> The core problem here is that NFSv4 and ext4 use different and largely >> incompatible ACL implementations. There is no way to accurately >> translate from one to the other in general (common specific examples >> can be converted). >> >> This means that either: >> 1/ overlayfs cannot use ext4 for upper and NFS for lower (or vice >> versa) or >> 2/ overlayfs need to accept that sometimes it cannot copy ACLs, and >> that is OK. >> >> Silently not copying the ACLs is probably not a good idea as it might >> result in inappropriate permissions being given away. > > For example? permissions given away to do what? > Note that ovl_permission() only check permissions of *mounter* > to read the lower NFS file and ovl_open()/ovl_read_iter() access > the lower file with *mounter* credentials. > > I might be wrong, but seems to me that once admin mounted > overlayfs with lower NFS, NFS ACLs are not being enforced at all > even before copy up. I guess it is just as well that copy-up fails then - if the lower-level permission check is being ignored. > >> So if the >> sysadmin wants this (and some clearly do), they need a way to >> explicitly say "I accept the risk". If only standard Unix permissions >> are used, there is no risk, so this seems reasonable. >> >> So I would like to propose a new option for overlayfs >> nocopyupacl: when overlayfs is copying a file (or directory etc) >> from the lower filesystem to the upper filesystem, it does not >> copy extended attributes with the "system." prefix. These are >> used for storing ACL information and this is sometimes not >> compatible between different filesystem types (e.g. ext4 and >> NFSv4). Standard Unix ownership permission flags (rwx) *are* >> copied so this option does not risk giving away inappropriate >> permissions unless the lowerfs uses unusual ACLs. >> >> > > I am wondering if it would make more sense for nfs to register a > security_inode_copy_up_xattr() hook. > That is the mechanism that prevents copying up other security.* > xattrs? No, I don't think that would make sense. Support some day support for nfs4 acls were added to ext4 (not a totally ridiculous suggestion). We would then want NFS to allow it's ACLs to be copied up. Thanks, NeilBrown > > Thanks, > Amir. --=-=-= Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEG8Yp69OQ2HB7X0l6Oeye3VZigbkFAlzKao8ACgkQOeye3VZi gblRlBAAvBfk2jX/vg9m1uaP0EEz3Ta0ixcKfA562CyVPtxCJ1i2folavvKXbA7i zUK9ZURimMkmGoN06wIepjCJRaaCA3G9Q2fw03Z2+LQdzecbfzsWKNQgITJ5IUP9 q3114hOw+oKFPMKDpJBYqwWQfP0gc7mTC114UhTm8gpBfbSwNVeNFzNYO+XX7cjx VLVvzjNXNgTcSRv3ojhcR3nKE29eCwGlQM4Adr0GEcvUW6lfh/6A89jEHegXmH+j AJ+15UjNSMNB2MXMT0hZ1GVj1DFPfSu64iP1ZRInVVnYGSphp0EB3atok65dDWU7 TxCgvHU1mOXb8wXY2zQxF+XxZ1Mw+70ADX2JVhFYqJ/aT4FKH9xeHg+AGgXZOv0s 0GhTLr5ffcVDLCcD+Q0MGvEMJDlVEwrjzt8gFNtXbhAQSumkURuDWqJlen+M6GAn jN0+qRbDZ3fKdlLQOLVdwgdeAxSZmLMPnnbNwt6REFiT7htF67sQUY1wA04lh4o0 rnodztakNYHAUdxM/9mUH66UZuWGvKG7ap+VHjawvboIW788iKLuhAz4PsFyBJW3 v+RMsD/4H2EvrSQN1IzeU5qz1HiPdsbF3QgkFLuciEpfIs8nkNKnnWViNC/hB7tn Q+VRDogKoYelNX3tlq4812N2EccBkTbQykyayhMiEvzugKsmDvA= =eO7x -----END PGP SIGNATURE----- --=-=-=--