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=-7.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 AEB69C433DB for ; Fri, 29 Jan 2021 02:51:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 58E4764DFF for ; Fri, 29 Jan 2021 02:51:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231517AbhA2CvZ (ORCPT ); Thu, 28 Jan 2021 21:51:25 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32862 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231470AbhA2CvX (ORCPT ); Thu, 28 Jan 2021 21:51:23 -0500 Received: from fieldses.org (fieldses.org [IPv6:2600:3c00:e000:2f7::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E31E5C061574 for ; Thu, 28 Jan 2021 18:50:42 -0800 (PST) Received: by fieldses.org (Postfix, from userid 2815) id D2A194599; Thu, 28 Jan 2021 21:50:41 -0500 (EST) DKIM-Filter: OpenDKIM Filter v2.11.0 fieldses.org D2A194599 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fieldses.org; s=default; t=1611888641; bh=/PNiZBSBHkdCLynmfVXpV/UcnWGC24yhrG6mM4fz0vA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=nfSRm87a+p97/ZmMnMh8VQ/0pmOv/vzQmLYrj6UN2aFBDo6fqtzHMFx6D04smqvYp vil+rYniVb3AEmDccW/VQcMTugZMqTNInx24eSJ9uFA4CGJc/e0/8ScrKP2gtKDSHC 19sNoaU6f1UOMmB6NGMwpHpqRQTinWX5TGVgAIuM= Date: Thu, 28 Jan 2021 21:50:41 -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: <20210129025041.GA12151@fieldses.org> References: <20210128223638.GE29887@fieldses.org> <95e5f9e4-76d4-08c4-ece3-35a10c06073b@vastdata.com> <20210129023527.GA11864@fieldses.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210129023527.GA11864@fieldses.org> User-Agent: Mutt/1.5.21 (2010-09-15) Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org On Thu, Jan 28, 2021 at 09:35:27PM -0500, bfields@fieldses.org wrote: > 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. So, I should have said in the changelog, apologies--the behavior without this patch is that when it gets a removexattr, the client sends a SETATTR with a bitmap claiming there's an ACL attribute, but a zero-length attribute value list, and the server (correctly) returns BADXDR. --b.