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=-17.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 29776C433DB for ; Fri, 29 Jan 2021 02:36:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DAE3E64DFA for ; Fri, 29 Jan 2021 02:36:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229757AbhA2CgN (ORCPT ); Thu, 28 Jan 2021 21:36:13 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57862 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229786AbhA2CgJ (ORCPT ); Thu, 28 Jan 2021 21:36:09 -0500 Received: from fieldses.org (fieldses.org [IPv6:2600:3c00:e000:2f7::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0F4E0C061573 for ; Thu, 28 Jan 2021 18:35:28 -0800 (PST) Received: by fieldses.org (Postfix, from userid 2815) id 7BD324599; Thu, 28 Jan 2021 21:35:27 -0500 (EST) DKIM-Filter: OpenDKIM Filter v2.11.0 fieldses.org 7BD324599 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fieldses.org; s=default; t=1611887727; bh=fKYk+bQMjc7+Pk1Fus0b+39ojugig6ZiA62cnbvlwSo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=b1iNwtWNaGyajoeSIQgdLzpEoiRbYPUQOB2XpxPh2UgiGB8Z5/FACo5kNrr3c9V/g yq+mqKUKAWFEA6b7D3TiWsjw+k2EWpJTmcPZn/EnXXjP9qxToZtYjJYISXliWs1MAS aVBAkLOb3ki25H5QN6o70o0y9sytO54ZwFnpHN8M= Date: Thu, 28 Jan 2021 21:35:27 -0500 From: "bfields@fieldses.org" To: Trond Myklebust Cc: "guy@vastdata.com" , "schumakeranna@gmail.com" , "linux-nfs@vger.kernel.org" Subject: Re: [PATCH] nfs: we don't support removing system.nfs4_acl Message-ID: <20210129023527.GA11864@fieldses.org> References: <20210128223638.GE29887@fieldses.org> <95e5f9e4-76d4-08c4-ece3-35a10c06073b@vastdata.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org On Fri, Jan 29, 2021 at 01:37:10AM +0000, Trond Myklebust wrote: > On Fri, 2021-01-29 at 01:34 +0200, guy keren wrote: > > On 1/29/21 12:36 AM, J. Bruce Fields wrote: > > From: "J. Bruce Fields" > > > > The NFSv4 protocol doesn't have any notion of reomoving an attribute, > > so > > removexattr(path,"system.nfs4_acl") doesn't make sense. > > > > There's no documented return value. Arguably it could be EOPNOTSUPP > > but > > I'm a little worried an application might take that to mean that we > > don't support ACLs or xattrs. How about EINVAL? > > > > Signed-off-by: J. Bruce Fields > > --- > >  fs/nfs/nfs4proc.c | 3 +++ > >  1 file changed, 3 insertions(+) > > > > diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c > > index 2f4679a62712..d50dea5f5723 100644 > > --- a/fs/nfs/nfs4proc.c > > +++ b/fs/nfs/nfs4proc.c > > @@ -5895,6 +5895,9 @@ static int __nfs4_proc_set_acl(struct inode > > *inode, const void *buf, size_t bufl > >   unsigned int npages = DIV_ROUND_UP(buflen, PAGE_SIZE); > >   int ret, i; > >   > > + /* You can't remove system.nfs4_acl: */ > > + if (buflen == 0) > > + return -EINVAL; > >   if (!nfs4_server_supports_acls(server)) > >   return -EOPNOTSUPP; > >   if (npages > ARRAY_SIZE(pages)) > > > > question: what happens if someone is attempting to create an empty > > ACL on a file? as far as i know, this is legal. > > won't you arrive into this position with a buflen of 0? it should be > > similar to 'chmod 0 '. > > > > Agreed. If the server doesn't support removing the ACL then it should > be up to it to enforce that condition. I see nothing in the NFS > protocol that says it is up to the NFS client to act as the enforcer > here. Agreed. Note that this patch doesn't prevent an application from setting a zero-length ACL. The xattr format is XDR with the first four bytes representing the number of ACEs, so you'd set a zero-length ACL by passing down a 4-byte all-zero buffer as the new value of the system.nfs4_acl xattr. A zero-length NULL buffer is what's used to implement removexattr: int __vfs_removexattr(struct dentry *dentry, const char *name) { ... return handler->set(handler, dentry, inode, name, NULL, 0, XATTR_REPLACE); } That's the case this patch covers. --b.