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=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 C1DB5C43219 for ; Thu, 2 May 2019 15:08:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 75E7520675 for ; Thu, 2 May 2019 15:08:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="maX0kka0" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726372AbfEBPI1 (ORCPT ); Thu, 2 May 2019 11:08:27 -0400 Received: from mail-it1-f194.google.com ([209.85.166.194]:54903 "EHLO mail-it1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726336AbfEBPI1 (ORCPT ); Thu, 2 May 2019 11:08:27 -0400 Received: by mail-it1-f194.google.com with SMTP id a190so3884735ite.4; Thu, 02 May 2019 08:08:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=vN+j4+nd5BKyao3Lvpqus6B/aYyzpgJNlMx+q2AjsvM=; b=maX0kka07S2TirIQcAeXMZI/A78EbHhVEa0CawKgApQa0vMzPqhvAJfIvbkvduHi6K Kwht2DoZWwI2uJ1dvudku2iCZlO5bozXFhz5ZovmQedJQBnlBq1WDlJ7ClStqXmfGvSp 9xSixbuXn21Yb/id8TBTo2yhTHpaR+2Ufj01A6BO64KEMo4l+MkyQ9f11jUwAJMXRmpc crROedOFVkDi+CXxFDtzpQeiI146nGbc1L0VesyE5qg1KWzlm5wBedOwTfagEzuoGYKx utAO7q71Gz9i7MKYIIumkyof+4nCEYL4axNNMHUdsVtY8C2aTIuyQc91PAcaAuOLKa6z 2LzQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=vN+j4+nd5BKyao3Lvpqus6B/aYyzpgJNlMx+q2AjsvM=; b=qp3lkCQNKjfcvBVxreJNGBjZbEL2BJ/MF1x9mzcUN50Dl+APkcPYmlad8ut6vhl0qw ualNFzmfB5uCV/Lt3gIQ/x8sGY4zQikWuH6MlLYNmM/ulaPOAYkmFIITb4mRnFQXGr8w 3yNp2cyCEKM9nA7ckc4RLNavwEx7hYTDyoNVM92YZfv/GTh5nW4gMugYhnxIjkHPvC45 SBuF6RPrV6GvrhFqLIOwdKKn08yh6i6qt4acPr25UseUkLyjEfUf++B1AMtwiyWaqDc1 +uEgmpmCqKyuXtF4SURSK+tn5O/4IMKpFDvXbb5gakNVWRIlieqUFGaKufuSypm7pxeZ 2Lqw== X-Gm-Message-State: APjAAAVZrV9eXc/ZuuJEuIcrKvJlbgdCZ+rGaSObO5mr0BsP1BRm3tWp pTWrca3ALCAbxJ3SC1btCLVZLMl8A0vmuIIjCFo= X-Google-Smtp-Source: APXvYqzRXnHs/jp8hUcRI6o4ZSLm1l+dCCRmqIRTdj0/iWnMR+SsBGvCQ1M/uMltF6DPwV8qgJIiNekygPL8hs5lW2M= X-Received: by 2002:a24:4ace:: with SMTP id k197mr2928742itb.46.1556809706149; Thu, 02 May 2019 08:08:26 -0700 (PDT) MIME-Version: 1.0 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> <875zqt4igg.fsf@notabene.neil.brown.name> In-Reply-To: From: =?UTF-8?Q?Andreas_Gr=C3=BCnbacher?= Date: Thu, 2 May 2019 17:08:14 +0200 Message-ID: Subject: Re: [PATCH] overlayfs: ignore empty NFSv4 ACLs in ext4 upperdir To: Miklos Szeredi Cc: Andreas Gruenbacher , NeilBrown , Amir Goldstein , "J. Bruce Fields" , Patrick Plagwitz , "linux-unionfs@vger.kernel.org" , Linux NFS list , Linux FS-devel Mailing List , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Am Do., 2. Mai 2019 um 16:28 Uhr schrieb Miklos Szeredi = : > On Thu, May 2, 2019 at 10:05 AM Andreas Gruenbacher = wrote: > > On Thu, 2 May 2019 at 05:57, NeilBrown wrote: > > > 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 wr= ote: > > > >> >> On Tue, Dec 6, 2016 at 11:08 AM, Miklos Szeredi wrote: > > > >> >> > 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 i= f 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 it= s own > > > >> >> >>> attribute already, so actually converting .) That way, over= layfs could > > > >> >> >>> still fail copying up files that have an actual ACL. It's s= till an > > > >> >> >>> ugly hack ... > > > >> >> >> > > > >> >> >> Actually, that kind of heuristic would make sense in the NFS= client > > > >> >> >> which could then hide the "system.nfs4_acl" attribute. > > > > I still think the nfs client could make this problem mostly go away by > > not exposing "system.nfs4_acl" xattrs when the acl is equivalent to > > the file mode. The richacl patches contain a workable abgorithm for > > that. The problem would remain for files that have an actual NFS4 ACL, > > which just cannot be mapped to a file mode or to POSIX ACLs in the > > general case, as well as for files that have a POSIX ACL. Mapping NFS4 > > ACL that used to be a POSIX ACL back to POSIX ACLs could be achieved > > in many cases as well, but the code would be quite messy. A better way > > seems to be to using a filesystem that doesn't support POSIX ACLs in > > the first place. Unfortunately, xfs doesn't allow turning off POSIX > > ACLs, for example. > > How about mounting NFSv4 with noacl? That should fix this issue, right? You'll still see permissions that differ from what the filesystem enforces, and copy-up would change that behavior. Andreas > Thanks, > Miklos > > > > > > > Andreas > > > > > >> >> > Even simpler would be if knfsd didn't send the attribute if n= ot > > > >> >> > necessary. Looks like there's code actively creating the nfs= 4_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_KERNE= L); > > > >> >> > > > > >> >> > 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 e= mail > > > >> 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 la= rgely > > > >> incompatible ACL implementations. There is no way to accurately > > > >> translate from one to the other in general (common specific examp= les > > > >> can be converted). > > > >> > > > >> This means that either: > > > >> 1/ overlayfs cannot use ext4 for upper and NFS for lower (or vi= ce > > > >> 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 m= ight > > > >> 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-lev= el > > > 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 permis= sions > > > >> 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 a= nd > > > >> NFSv4). Standard Unix ownership permission flags (rwx) *a= re* > > > >> copied so this option does not risk giving away inappropri= ate > > > >> 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 tota= lly > > > ridiculous suggestion). We would then want NFS to allow it's ACLs to= be > > > copied up. > > > > > > Thanks, > > > NeilBrown > > > > > > > > > > > > > > Thanks, > > > > Amir.