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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0A407C433EF for ; Sat, 16 Jul 2022 02:33:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230010AbiGPCdf (ORCPT ); Fri, 15 Jul 2022 22:33:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59050 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229507AbiGPCde (ORCPT ); Fri, 15 Jul 2022 22:33:34 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5F42618377; Fri, 15 Jul 2022 19:33:33 -0700 (PDT) Received: from dggpeml500021.china.huawei.com (unknown [172.30.72.57]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4LlBzc6WHpz1M7tN; Sat, 16 Jul 2022 10:30:52 +0800 (CST) Received: from [10.174.177.174] (10.174.177.174) by dggpeml500021.china.huawei.com (7.185.36.21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Sat, 16 Jul 2022 10:33:30 +0800 Message-ID: <425ab528-7d9a-975a-7f4c-5f903cedd8bc@huawei.com> Date: Sat, 16 Jul 2022 10:33:30 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.8.1 Subject: Re: [PATCH 4.19] ext4: fix race condition between ext4_ioctl_setflags and ext4_fiemap To: Greg KH CC: , , , , , , , , , , , , Hulk Robot , Baokun Li References: <20220715023928.2701166-1-libaokun1@huawei.com> From: Baokun Li In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.174] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpeml500021.china.huawei.com (7.185.36.21) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 在 2022/7/15 22:10, Greg KH 写道: > On Fri, Jul 15, 2022 at 10:39:28AM +0800, Baokun Li wrote: >> This patch and problem analysis is based on v4.19 LTS. >> The d3b6f23f7167("ext4: move ext4_fiemap to use iomap framework") patch >> is incorporated in v5.7-rc1. This patch avoids this problem by switching >> to iomap in ext4_fiemap. >> >> Hulk Robot reported a BUG on stable 4.19.252: >> ================================================================== >> kernel BUG at fs/ext4/extents_status.c:762! >> invalid opcode: 0000 [#1] SMP KASAN PTI >> CPU: 7 PID: 2845 Comm: syz-executor Not tainted 4.19.252 #46 >> RIP: 0010:ext4_es_cache_extent+0x30e/0x370 >> [...] >> Call Trace: >> ext4_cache_extents+0x238/0x2f0 >> ext4_find_extent+0x785/0xa40 >> ext4_fiemap+0x36d/0xe90 >> do_vfs_ioctl+0x6af/0x1200 >> [...] >> ================================================================== >> >> Above issue may happen as follows: >> ------------------------------------- >> cpu1 cpu2 >> _____________________|_____________________ >> do_vfs_ioctl >> ext4_ioctl >> ext4_ioctl_setflags >> ext4_ind_migrate >> do_vfs_ioctl >> ioctl_fiemap >> ext4_fiemap >> ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS) >> ext4_fill_fiemap_extents >> down_write(&EXT4_I(inode)->i_data_sem); >> ext4_ext_check_inode >> ext4_clear_inode_flag(inode, EXT4_INODE_EXTENTS) >> memset(ei->i_data, 0, sizeof(ei->i_data)) >> up_write(&EXT4_I(inode)->i_data_sem); >> down_read(&EXT4_I(inode)->i_data_sem); >> ext4_find_extent >> ext4_cache_extents >> ext4_es_cache_extent >> BUG_ON(end < lblk) >> >> We can easily reproduce this problem with the syzkaller testcase: >> ``` >> 02:37:07 executing program 3: >> r0 = openat(0xffffffffffffff9c, &(0x7f0000000040)='./file0\x00', 0x26e1, 0x0) >> ioctl$FS_IOC_FSSETXATTR(r0, 0x40086602, &(0x7f0000000080)={0x17e}) >> mkdirat(0xffffffffffffff9c, &(0x7f00000000c0)='./file1\x00', 0x1ff) >> r1 = openat(0xffffffffffffff9c, &(0x7f0000000100)='./file1\x00', 0x0, 0x0) >> ioctl$FS_IOC_FIEMAP(r1, 0xc020660b, &(0x7f0000000180)={0x0, 0x1, 0x0, 0xef3, 0x6, []}) (async, rerun: 32) >> ioctl$FS_IOC_FSSETXATTR(r1, 0x40086602, &(0x7f0000000140)={0x17e}) (rerun: 32) >> ``` >> >> To solve this issue, we use __generic_block_fiemap() instead of >> generic_block_fiemap() and add inode_lock_shared to avoid race condition. >> >> Reported-by: Hulk Robot >> Signed-off-by: Baokun Li >> --- >> fs/ext4/extents.c | 15 +++++++++++---- >> 1 file changed, 11 insertions(+), 4 deletions(-) > What is the git commit id of this change in Linus's tree? > > If it is not in Linus's tree, why not? > > confused, > > greg k-h > . This patch does not exist in the Linus' tree. This problem persists until the patch d3b6f23f7167("ext4: move ext4_fiemap to use iomap framework") is incorporated in v5.7-rc1. However, this problem can be found by asserting  after patch 4068664e3cd2 ("ext4: fix extent_status fragmentation for plain files") is incorporated into v5.6-rc1. If someone don't want to convert ext4_fiemap to iomap, this patch may help. I also CC linux-ext4 in hopes of getting some advice. Feel free to improve it if something wrong. Thanks a lot! -- With Best Regards, Baokun Li