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=-0.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 54BEAC43219 for ; Thu, 2 May 2019 14:29:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1C1F4205F4 for ; Thu, 2 May 2019 14:29:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="key not found in DNS" (0-bit key) header.d=szeredi.hu header.i=@szeredi.hu header.b="com3sCaU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726350AbfEBO24 (ORCPT ); Thu, 2 May 2019 10:28:56 -0400 Received: from mail-it1-f193.google.com ([209.85.166.193]:40251 "EHLO mail-it1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726327AbfEBO24 (ORCPT ); Thu, 2 May 2019 10:28:56 -0400 Received: by mail-it1-f193.google.com with SMTP id k64so3699153itb.5 for ; Thu, 02 May 2019 07:28:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=szeredi.hu; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=BqHJ4mKCqV4ZGSDIdcnHrlBfq1c/O0ILprJjcbsuKxg=; b=com3sCaUbNmDKYX9/c5R+Szvf04X7EZ4tn/wfCS/BU0LTNv6c+nRVC4wASCSoqTjhz Cn4K7TqAYCy6JbLvppR/ADv/CBq8EBhfNp9GTjKKe96GJewCZvF4Pch1lfqzBBmBFmsC hot8x00MO/pDkp48ppQmvOT2nA1ueTrdl+wlE= 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=BqHJ4mKCqV4ZGSDIdcnHrlBfq1c/O0ILprJjcbsuKxg=; b=KiBPPZXSgk8CsgJxxYltdmQ7Q30AIEOjj3Pxfl9QO6GyyUp6p6BkS0ushFuTqOSUmK lV12z0ry0U9ojxwoxk3sxY4KWwALnQBHqsCYzzPGambu6roeS2TZTzKfEaitKpR7+EDw 0ecu3LS7KazSYWUXLitZFzGRFP8j3NAIlJvOQOVVDvJIrBAfylZyupCZd6pOfwqUcVHO q7S3sUd832EBzOaN4g9GhsOFXRcwNylkNxhUkmrDWM9Wkm/zWYey5pHtJTRi6Jt2Ulcz j3xtbC2SSZVuTOipxUv+0v0t5G3RnX7Y1FODCT4PYayIHraOPgypbN2lq+nN2VCKKMOw dA/w== X-Gm-Message-State: APjAAAXf+Zaqi/IeJzSd9SWaPEUrpRnvn1dNqbSnNctbUpfAuUklY7Ne at/T3zCGDlDBvmSNZ3DvrBRbx+XWuAWqxe/33Ku+Iw== X-Google-Smtp-Source: APXvYqwiDaSe7oR13TqnAe4ifdblvh6sX0UjdKbinWlL2NINaz4O5wVQDsGbSp4jFuCH25uLqaqshcY7ngDOXzPt63U= X-Received: by 2002:a24:b342:: with SMTP id z2mr2342309iti.121.1556807335385; Thu, 02 May 2019 07:28:55 -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: Miklos Szeredi Date: Thu, 2 May 2019 10:28:44 -0400 Message-ID: Subject: Re: [PATCH] overlayfs: ignore empty NFSv4 ACLs in ext4 upperdir To: Andreas Gruenbacher Cc: NeilBrown , Amir Goldstein , "J. Bruce Fields" , =?UTF-8?Q?Andreas_Gr=C3=BCnbacher?= , 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-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org On Thu, May 2, 2019 at 10:05 AM Andreas Gruenbacher w= rote: > > 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 wrot= e: > > >> >> 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 if = a > > >> >> >>> system.nfs4_acl value is equivalent to a file mode, and to ig= nore the > > >> >> >>> attribute in that case. (The file mode is transmitted in its = own > > >> >> >>> attribute already, so actually converting .) That way, overla= yfs could > > >> >> >>> still fail copying up files that have an actual ACL. It's sti= ll an > > >> >> >>> ugly hack ... > > >> >> >> > > >> >> >> Actually, that kind of heuristic would make sense in the NFS c= lient > > >> >> >> 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? Thanks, Miklos > > Andreas > > > >> >> > 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 th= e > > >> > 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 ema= il > > >> thread. > > >> Unfortunately it didn't resolve anything. Maybe I can help kick th= ings > > >> along??? > > >> > > >> The core problem here is that NFSv4 and ext4 use different and larg= ely > > >> incompatible ACL implementations. There is no way to accurately > > >> translate from one to the other in general (common specific example= s > > >> 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, a= nd > > >> that is OK. > > >> > > >> Silently not copying the ACLs is probably not a good idea as it mig= ht > > >> 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 permissi= ons > > >> 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 et= c) > > >> from the lower filesystem to the upper filesystem, it does n= ot > > >> copy extended attributes with the "system." prefix. These a= re > > >> 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 inappropriat= e > > >> 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 totall= y > > ridiculous suggestion). We would then want NFS to allow it's ACLs to b= e > > copied up. > > > > Thanks, > > NeilBrown > > > > > > > > > > Thanks, > > > Amir.