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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 31E66C43334 for ; Mon, 3 Sep 2018 08:01:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C5F0420856 for ; Mon, 3 Sep 2018 08:01:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C5F0420856 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=mail.parknet.co.jp Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726090AbeICMUF (ORCPT ); Mon, 3 Sep 2018 08:20:05 -0400 Received: from mail.parknet.co.jp ([210.171.160.6]:54844 "EHLO mail.parknet.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725898AbeICMUF (ORCPT ); Mon, 3 Sep 2018 08:20:05 -0400 Received: from ibmpc.myhome.or.jp (server.parknet.ne.jp [210.171.168.39]) by mail.parknet.co.jp (Postfix) with ESMTPSA id 813DF15AF4B; Mon, 3 Sep 2018 17:01:05 +0900 (JST) Received: from devron.myhome.or.jp (foobar@devron.myhome.or.jp [192.168.0.3]) by ibmpc.myhome.or.jp (8.15.2/8.15.2/Debian-11) with ESMTPS id w83814mw019015 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 3 Sep 2018 17:01:05 +0900 Received: from devron.myhome.or.jp (foobar@localhost [127.0.0.1]) by devron.myhome.or.jp (8.15.2/8.15.2/Debian-11) with ESMTPS id w83814OP001866 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 3 Sep 2018 17:01:04 +0900 Received: (from hirofumi@localhost) by devron.myhome.or.jp (8.15.2/8.15.2/Submit) id w83813Ev001865; Mon, 3 Sep 2018 17:01:03 +0900 From: OGAWA Hirofumi To: Pali =?iso-8859-1?Q?Roh=E1r?= Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH] fat: Relax checks for sector size and media type References: <20180902131932.11558-1-pali.rohar@gmail.com> <87bm9ft5h5.fsf@mail.parknet.co.jp> <20180903074005.7e3guj24ksq2l44c@pali> Date: Mon, 03 Sep 2018 17:01:03 +0900 In-Reply-To: <20180903074005.7e3guj24ksq2l44c@pali> ("Pali =?iso-8859-1?Q?Roh=E1r=22's?= message of "Mon, 3 Sep 2018 09:40:05 +0200") Message-ID: <874lf7t3gg.fsf@mail.parknet.co.jp> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Pali Rohár writes: >> Just relaxing validation doesn't work. The block layer doesn't support >> smaller than 512, and lager than PAGE_SIZE. (And in specification, fat >> doesn't support lager than 4096.) > > Hi! I just sent this patch for discussion, with links to (now open > source) Windows implementation. I guess that Windows driver > implementation is more "authoritative" then Microsoft's own > specification. It is known that Windows implementation does not match > Microsoft specification. > > I know at least 3 FAT specifications (MS EFI FAT, MS/SD card FAT, > ECMA-107) and you are right that Microsoft's one does not allow sector > sizes larger then 4096. > > If there is limitation by block layer, then: > > 1) Why we do not check for PAGE_SIZE? That source seems to check power_of_2(size) and 128 <= size <= 4096. Rather why do you want to support larger than 4096? Or I'm missing something? > 2) Is check in fat driver really needed (if block layer checks it)? Yes, isolating block layer error and fat format error to be better error report. -- OGAWA Hirofumi