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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 65BF5CA9EC0 for ; Mon, 28 Oct 2019 12:36:35 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 68E2D208C0 for ; Mon, 28 Oct 2019 12:36:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 68E2D208C0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 471vNH5ytWzDr3G for ; Mon, 28 Oct 2019 23:36:31 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=huawei.com (client-ip=45.249.212.32; helo=huawei.com; envelope-from=yuchao0@huawei.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=huawei.com Received: from huawei.com (szxga06-in.huawei.com [45.249.212.32]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 471vN14qLPzDqVj for ; Mon, 28 Oct 2019 23:36:13 +1100 (AEDT) Received: from DGGEMS403-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id 21712E3E9323C23C9E06; Mon, 28 Oct 2019 20:36:08 +0800 (CST) Received: from [10.134.22.195] (10.134.22.195) by smtp.huawei.com (10.3.19.203) with Microsoft SMTP Server (TLS) id 14.3.439.0; Mon, 28 Oct 2019 20:36:01 +0800 Subject: Re: [PATCH v4] erofs: support superblock checksum To: Gao Xiang References: <20191022180620.19638-1-pratikshinde320@gmail.com> <20191023040557.230886-1-gaoxiang25@huawei.com> <20191023084536.GA16289@architecture4> From: Chao Yu Message-ID: Date: Mon, 28 Oct 2019 20:36:00 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20191023084536.GA16289@architecture4> Content-Type: text/plain; charset="windows-1252" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.134.22.195] X-CFilter-Loop: Reflected X-BeenThere: linux-erofs@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Development of Linux EROFS file system List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Gao Xiang , linux-erofs@lists.ozlabs.org, linux-kernel@vger.kernel.org Errors-To: linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org Sender: "Linux-erofs" On 2019/10/23 16:45, Gao Xiang wrote: > Hi Chao, > > On Wed, Oct 23, 2019 at 04:15:29PM +0800, Chao Yu wrote: >> Hi, Xiang, Pratik, >> >> On 2019/10/23 12:05, Gao Xiang wrote: > > > >>> } >>> >>> +static int erofs_superblock_csum_verify(struct super_block *sb, void *sbdata) >>> +{ >>> + struct erofs_super_block *dsb; >>> + u32 expected_crc, nblocks, crc; >>> + void *kaddr; >>> + struct page *page; >>> + int i; >>> + >>> + dsb = kmemdup(sbdata + EROFS_SUPER_OFFSET, >>> + EROFS_BLKSIZ - EROFS_SUPER_OFFSET, GFP_KERNEL); >>> + if (!dsb) >>> + return -ENOMEM; >>> + >>> + expected_crc = le32_to_cpu(dsb->checksum); >>> + nblocks = le32_to_cpu(dsb->chksum_blocks); >> >> Now, we try to use nblocks's value before checking its validation, I guess fuzz >> test can easily make the value extreme larger, result in checking latter blocks >> unnecessarily. >> >> IMO, we'd better >> 1. check validation of superblock to make sure all fields in sb are valid >> 2. use .nblocks to count and check payload blocks following sb > > That is quite a good point. :-) > > My first thought is to check the following payloads of sb (e.g, some per-fs > metadata should be checked at mount time together. or for small images, check > the whole image at the mount time) as well since if we introduce a new feature > to some kernel version, forward compatibility needs to be considered. So it's > better to make proper scalability, for this case, we have some choices: > 1) limit `chksum_blocks' upbound at runtime (e.g. refuse >= 65536 blocks, > totally 256M.) > 2) just get rid of the whole `chksum_blocks' mess and checksum the first 4k > at all, don't consider any latter scalability. Xiang, sorry for later reply... I prefer method 2), let's enable chksum feature only on superblock first, chksum_blocks feature can be added later. Thanks, > > Some perferred idea about this? I plan to release erofs-utils v1.0 tomorrow > and hold up this feature for the next erofs-utils release, but I think we can > get it ready for v5.5 since it is not quite complex feature... > > Thanks, > Gao Xiang > > . >