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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 AD58DC433E4 for ; Sun, 26 Jul 2020 16:37:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 96E2520714 for ; Sun, 26 Jul 2020 16:37:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726701AbgGZQhQ (ORCPT ); Sun, 26 Jul 2020 12:37:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33596 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725949AbgGZQhQ (ORCPT ); Sun, 26 Jul 2020 12:37:16 -0400 Received: from ZenIV.linux.org.uk (zeniv.linux.org.uk [IPv6:2002:c35c:fd02::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A8DA5C0619D2; Sun, 26 Jul 2020 09:37:15 -0700 (PDT) Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jzjeB-00367e-9C; Sun, 26 Jul 2020 16:37:11 +0000 Date: Sun, 26 Jul 2020 17:37:11 +0100 From: Al Viro To: Christoph Hellwig Cc: x86@kernel.org, Jan Kara , linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, linux-arch@vger.kernel.org Subject: Re: [PATCH 4/4] quota: simplify the quotactl compat handling Message-ID: <20200726163711.GU2786714@ZenIV.linux.org.uk> References: <20200726160401.311569-1-hch@lst.de> <20200726160401.311569-5-hch@lst.de> <20200726163214.GS2786714@ZenIV.linux.org.uk> <20200726163422.GA24657@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200726163422.GA24657@lst.de> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Sun, Jul 26, 2020 at 06:34:22PM +0200, Christoph Hellwig wrote: > On Sun, Jul 26, 2020 at 05:32:14PM +0100, Al Viro wrote: > > > +static int compat_copy_fs_qfilestat(struct compat_fs_qfilestat __user *to, > > > + struct fs_qfilestat *from) > > > +{ > > > + if (copy_to_user(to, from, sizeof(*to)) || > > > + put_user(from->qfs_nextents, &to->qfs_nextents)) > > > + return -EFAULT; > > > + return 0; > > > +} > > > > do we have any need of that put_user()? Note that you don't even call > > that thing unless compat_need_64bit_alignment_fixup() is true. And AFAICS > > all such cases are little-endian... > > The main reason it is there is to preserve the previous semantics. > And no, I don't think we actually need it on x86. But what if some > poor souls adds a BE version that needs this? E.g. arm oabi has similar > weird alignment, and now imagine someone adding arm64 compat code for > that.. I'd probably add /* just in case some poor sod fucks up the same way for big-endian biarch */ next to that put_user(), then ;-)