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=-0.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 DF4EEC04AAB for ; Tue, 7 May 2019 00:25:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A853A206A3 for ; Tue, 7 May 2019 00:25:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726476AbfEGAZJ (ORCPT ); Mon, 6 May 2019 20:25:09 -0400 Received: from mx2.suse.de ([195.135.220.15]:51406 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726073AbfEGAZJ (ORCPT ); Mon, 6 May 2019 20:25:09 -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 72C33AE5A; Tue, 7 May 2019 00:25:07 +0000 (UTC) From: NeilBrown To: "J. Bruce Fields" Date: Tue, 07 May 2019 10:24:58 +1000 Cc: 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: <20190503153531.GJ12608@fieldses.org> References: <20161205162559.GB17517@fieldses.org> <266c571f-e4e2-7c61-5ee2-8ece0c2d06e9@web.de> <20161206185806.GC31197@fieldses.org> <87bm0l4nra.fsf@notabene.neil.brown.name> <20190503153531.GJ12608@fieldses.org> Message-ID: <87woj3157p.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 Fri, May 03 2019, J. Bruce Fields wrote: > On Thu, May 02, 2019 at 12:02:33PM +1000, NeilBrown wrote: >> On Tue, Dec 06 2016, J. Bruce Fields wrote: >>=20 >> > 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? >> >>=20 >> >> 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.) >> >>=20 >> >> Andreas >>=20 >> 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??? >>=20 >> 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). >>=20 >> 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. >>=20 >> Silently not copying the ACLs is probably not a good idea as it might >> result in inappropriate permissions being given away. So if the >> sysadmin wants this (and some clearly do), they need a way to >> explicitly say "I accept the risk". > > So, I feel like silently copying ACLs up *also* carries a risk, if that > means switching from server-enforcement to client-enforcement of those > permissions. Interesting perspective .... though doesn't NFSv4 explicitly allow client-side ACL enforcement in the case of delegations? Not sure how relevant that is.... It seems to me we have two options: 1/ declare the NFSv4 doesn't work as a lower layer for overlayfs and recommend people use NFSv3, or 2/ Modify overlayfs to work with NFSv4 by ignoring nfsv4 ACLs either 2a/ always - and ignore all other acls and probably all system. xattrs, or 2b/ based on a mount option that might be 2bi/ general "noacl" or might be 2bii/ explicit "noxattr=3Dsystem.nfs4acl" =20 I think that continuing to discuss the miniature of the options isn't going to help. No solution is perfect - we just need to clearly document the implications of whatever we come up with. I lean towards 2a, but I be happy with with any '2' and '1' won't kill me. Do we have a vote? Or does someone make an executive decision?? 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