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,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 41D47C43219 for ; Thu, 2 May 2019 02:55:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 054562086C for ; Thu, 2 May 2019 02:55:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="NNca5O+W" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726231AbfEBCzF (ORCPT ); Wed, 1 May 2019 22:55:05 -0400 Received: from mail-yw1-f66.google.com ([209.85.161.66]:40378 "EHLO mail-yw1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726205AbfEBCzF (ORCPT ); Wed, 1 May 2019 22:55:05 -0400 Received: by mail-yw1-f66.google.com with SMTP id t79so510484ywc.7; Wed, 01 May 2019 19:55:04 -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=z26n6/sH1AsDLpioQphX4q8VPU5RJ6kDUqodat8Mtow=; b=NNca5O+WSrABeS7FxwX2kVyi55yKQZ3Y0LgWmt/HcJXj4uY1JAUHblmApUu4o+Ci+s xWyL61X7MmIpAYoUr07WZD3vGP9xoPa0uM1nf1w7pgLgA4bD94jozmXKMYhpU6vHx9RK PpsfYnjaeLfrjJ0uc7SnPZpmQcetdMuJh2eMZZ2KGY1FiQGCdRRh8kCW8mfY44M9U46q 1Z7qjI+oZ+DTvgMGWlWhYajGM5Cg1tSztOL8Mv1xBSSqJMuOMwa3ObGCnPbJoJHeQlM4 YA9poXCVtSl9iVUyrEAsmMR+ACiDbmArDwl77rypSOCxY9HwP2itpZzFM0SSXRRY3Lhf H5Mg== 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=z26n6/sH1AsDLpioQphX4q8VPU5RJ6kDUqodat8Mtow=; b=k+Dqx0mjLyp74WzDDLcdFOC6yfNNjN/+ixbr5tIX9P53aablHP0X05mG1bpzPhfejT cncR3lY0EYAETROVsxTF7ySxfEzfjnezqMVvHpfsrPzPpMBkdHV7scvmbF88055EJenj 9pmnMyH1LwwQUJDOwsHQPXeY9F7GnZO9RI/SuZ1IW2VAy0vC4E219Uffrf3JYW2R/2Iy ZggIwubbwhkRbxjyq/mtDrnV5WxPxfIKcOqNUqQvTvgS++KoiedNhmcNEGP4hKhVqG22 +g22/wyzZPo1TYit02DRDETycs781pkpvB0icfgil2XeyTMXcE5hPuPAnYUItR7xF+ZO BJoQ== X-Gm-Message-State: APjAAAUTDB28aAInIa60i5mWuguboq/99SsntZb9NsDa2Os+VDGLwJTl BGMsTtHkfthv77E7bo9QVHcxBGFRcScXAKXkyIU= X-Google-Smtp-Source: APXvYqznaWNQLzQJptPPiF6oL+1IzIuegKrmT2CGGjSizksqtM7XGR6nr9+kccqVb+vnJbWv3cWxnjocNb/7rtuT1bY= X-Received: by 2002:a25:d64a:: with SMTP id n71mr1069731ybg.462.1556765703443; Wed, 01 May 2019 19:55:03 -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> In-Reply-To: <87bm0l4nra.fsf@notabene.neil.brown.name> From: Amir Goldstein Date: Wed, 1 May 2019 22:54:52 -0400 Message-ID: Subject: Re: [PATCH] overlayfs: ignore empty NFSv4 ACLs in ext4 upperdir To: NeilBrown Cc: "J. Bruce Fields" , Andreas Gruenbacher , Miklos Szeredi , =?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 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 wr= ote: > >> > 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 c= ould > >> >>> 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 o= n > >> > 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. > 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? Thanks, Amir.