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 79ECAC54EBC for ; Tue, 10 Jan 2023 11:49:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235744AbjAJLtw (ORCPT ); Tue, 10 Jan 2023 06:49:52 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42954 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238055AbjAJLtY (ORCPT ); Tue, 10 Jan 2023 06:49:24 -0500 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3E821559D3; Tue, 10 Jan 2023 03:49:22 -0800 (PST) Received: from dggpeml500021.china.huawei.com (unknown [172.30.72.54]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4Nrpw22cw9z16MdB; Tue, 10 Jan 2023 19:47:46 +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 15.1.2375.34; Tue, 10 Jan 2023 19:49:19 +0800 Message-ID: <6cad72af-45f4-7f40-64b6-c24aee70b312@huawei.com> Date: Tue, 10 Jan 2023 19:49:19 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.1.2 Subject: Re: [PATCH] ext4: fix task hung in ext4_xattr_delete_inode Content-Language: en-US To: Jan Kara CC: , , , , , , , References: <20230110042709.2136336-1-libaokun1@huawei.com> <20230110113407.ymamyqmg2rw6zfzu@quack3> From: Baokun Li In-Reply-To: <20230110113407.ymamyqmg2rw6zfzu@quack3> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.174] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpeml500021.china.huawei.com (7.185.36.21) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On 2023/1/10 19:34, Jan Kara wrote: > On Tue 10-01-23 12:27:09, Baokun Li wrote: >> Syzbot reported a hung task problem: >> ================================================================== >> INFO: task syz-executor232:5073 blocked for more than 143 seconds. >> Not tainted 6.2.0-rc2-syzkaller-00024-g512dee0c00ad #0 >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> task:syz-exec232 state:D stack:21024 pid:5073 ppid:5072 flags:0x00004004 >> Call Trace: >> >> context_switch kernel/sched/core.c:5244 [inline] >> __schedule+0x995/0xe20 kernel/sched/core.c:6555 >> schedule+0xcb/0x190 kernel/sched/core.c:6631 >> __wait_on_freeing_inode fs/inode.c:2196 [inline] >> find_inode_fast+0x35a/0x4c0 fs/inode.c:950 >> iget_locked+0xb1/0x830 fs/inode.c:1273 >> __ext4_iget+0x22e/0x3ed0 fs/ext4/inode.c:4861 >> ext4_xattr_inode_iget+0x68/0x4e0 fs/ext4/xattr.c:389 >> ext4_xattr_inode_dec_ref_all+0x1a7/0xe50 fs/ext4/xattr.c:1148 >> ext4_xattr_delete_inode+0xb04/0xcd0 fs/ext4/xattr.c:2880 >> ext4_evict_inode+0xd7c/0x10b0 fs/ext4/inode.c:296 >> evict+0x2a4/0x620 fs/inode.c:664 >> ext4_orphan_cleanup+0xb60/0x1340 fs/ext4/orphan.c:474 >> __ext4_fill_super fs/ext4/super.c:5516 [inline] >> ext4_fill_super+0x81cd/0x8700 fs/ext4/super.c:5644 >> get_tree_bdev+0x400/0x620 fs/super.c:1282 >> vfs_get_tree+0x88/0x270 fs/super.c:1489 >> do_new_mount+0x289/0xad0 fs/namespace.c:3145 >> do_mount fs/namespace.c:3488 [inline] >> __do_sys_mount fs/namespace.c:3697 [inline] >> __se_sys_mount+0x2d3/0x3c0 fs/namespace.c:3674 >> do_syscall_x64 arch/x86/entry/common.c:50 [inline] >> do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 >> entry_SYSCALL_64_after_hwframe+0x63/0xcd >> RIP: 0033:0x7fa5406fd5ea >> RSP: 002b:00007ffc7232f968 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5 >> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fa5406fd5ea >> RDX: 0000000020000440 RSI: 0000000020000000 RDI: 00007ffc7232f970 >> RBP: 00007ffc7232f970 R08: 00007ffc7232f9b0 R09: 0000000000000432 >> R10: 0000000000804a03 R11: 0000000000000202 R12: 0000000000000004 >> R13: 0000555556a7a2c0 R14: 00007ffc7232f9b0 R15: 0000000000000000 >> >> ================================================================== >> >> The problem is that the inode contains an xattr entry with ea_inum of 15 >> when cleaning up an orphan inode <15>. When evict inode <15>, the reference >> counting of the corresponding EA inode is decreased. When EA inode <15> is >> found by find_inode_fast() in __ext4_iget(), it is found that the EA inode >> holds the I_FREEING flag and waits for the EA inode to complete deletion. >> As a result, when inode <15> is being deleted, we wait for inode <15> to >> complete the deletion, resulting in an infinite loop and triggering Hung >> Task. To solve this problem, we only need to check whether the ino of EA >> inode and parent is the same before getting EA inode. >> >> Link: https://syzkaller.appspot.com/bug?extid=77d6fcc37bbb92f26048 >> Reported-by: syzbot+77d6fcc37bbb92f26048@syzkaller.appspotmail.com >> Signed-off-by: Baokun Li >> --- >> fs/ext4/xattr.c | 7 +++++++ >> 1 file changed, 7 insertions(+) >> >> diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c >> index 7decaaf27e82..9ff8fcf78bb8 100644 >> --- a/fs/ext4/xattr.c >> +++ b/fs/ext4/xattr.c >> @@ -386,6 +386,13 @@ static int ext4_xattr_inode_iget(struct inode *parent, unsigned long ea_ino, >> struct inode *inode; >> int err; >> > Perhaps add a comment here like: > > /* > * We have to check for this corruption early as otherwise > * iget_locked() could wait indefinitely for the state of our > * parent inode. > */ Totally agree! Very accurate comment! >> + if (parent->i_ino == ea_ino) { >> + ext4_error(parent->i_sb, >> + "Parent and EA inode have the same ino %lu", ea_ino); >> + err = -EUCLEAN; > ^^ I prefer -EFSCORRUPTED here. It is the same > value but more descriptive name :). OK! I will replace EUCLEAN with EFSCORRUPTED in v2. >> + goto error; > ^^ Just "return err" here. This will try to iput() > uninitialized pointer. > > Honza > Indeed! I'm sorry I didn't notice this uninitialized variable. Thank you very much for your review！ I will send a patch V2 with the changes suggested by you. -- With Best Regards, Baokun Li .