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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, 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 17A0FC3A59E for ; Mon, 26 Aug 2019 08:31:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EA5502080C for ; Mon, 26 Aug 2019 08:31:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729678AbfHZIbq (ORCPT ); Mon, 26 Aug 2019 04:31:46 -0400 Received: from szxga07-in.huawei.com ([45.249.212.35]:58852 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726747AbfHZIbq (ORCPT ); Mon, 26 Aug 2019 04:31:46 -0400 Received: from DGGEMS409-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id D0093D5AD12F44246E56; Mon, 26 Aug 2019 16:31:44 +0800 (CST) Received: from [127.0.0.1] (10.177.244.145) by DGGEMS409-HUB.china.huawei.com (10.3.19.209) with Microsoft SMTP Server id 14.3.439.0; Mon, 26 Aug 2019 16:31:42 +0800 Subject: Re: [PATCH v5] ext4: fix potential use after free in system zone via remount with noblock_validity To: "Theodore Y. Ts'o" References: <1565869639-105420-1-git-send-email-yi.zhang@huawei.com> <20190825034000.GE5163@mit.edu> <20190826025612.GB4918@mit.edu> CC: , , From: "zhangyi (F)" Message-ID: <33767946-1e6f-5165-94b3-46e2da15172f@huawei.com> Date: Mon, 26 Aug 2019 16:31:41 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <20190826025612.GB4918@mit.edu> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-Originating-IP: [10.177.244.145] X-CFilter-Loop: Reflected Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On 2019/8/26 10:56, Theodore Y. Ts'o Wrote: > I added a missing rcu_read_lock() to prevent a suspicious RCU > warning when CONFIG_PROVE_RCU is enabled: > > diff --git a/fs/ext4/block_validity.c b/fs/ext4/block_validity.c > index 003dc1dc2da3..f7bc914a74df 100644 > --- a/fs/ext4/block_validity.c > +++ b/fs/ext4/block_validity.c > @@ -330,11 +330,13 @@ void ext4_release_system_zone(struct super_block *sb) > { > struct ext4_system_blocks *system_blks; > > + rcu_read_lock(); > system_blks = rcu_dereference(EXT4_SB(sb)->system_blks); > rcu_assign_pointer(EXT4_SB(sb)->system_blks, NULL); > > if (system_blks) > call_rcu(&system_blks->rcu, ext4_destroy_system_zone); > + rcu_read_unlock(); > } > > int ext4_data_block_valid(struct ext4_sb_info *sbi, ext4_fsblk_t start_blk, > Hi Ted， Sorry about missing this warning, I think switch to use: system_blks = rcu_dereference_raw(EXT4_SB(sb)->system_blks); or system_blks = rcu_dereference_protected(EXT4_SB(sb)->system_blks, true); is enough to fix this waring, am I missing something? Thanks, Yi.