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 16FA4C77B73 for ; Mon, 5 Jun 2023 14:10:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234289AbjFEOKf (ORCPT ); Mon, 5 Jun 2023 10:10:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36662 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234588AbjFEOJv (ORCPT ); Mon, 5 Jun 2023 10:09:51 -0400 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D387710D4 for ; Mon, 5 Jun 2023 07:08:57 -0700 (PDT) Received: from canpemm500010.china.huawei.com (unknown [172.30.72.54]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4QZb5Y1bVtzLm1k; Mon, 5 Jun 2023 22:07:13 +0800 (CST) Received: from [10.174.178.185] (10.174.178.185) by canpemm500010.china.huawei.com (7.192.105.118) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.23; Mon, 5 Jun 2023 22:08:53 +0800 Subject: Re: [PATCH 1/2] quota: fix null-ptr-deref in ext4_acquire_dquot() To: Jan Kara References: <20230527014018.47396-1-yebin10@huawei.com> <20230527014018.47396-2-yebin10@huawei.com> <20230530095726.t2grmww5rzofx5gp@quack3> <647ADA33.5010508@huawei.com> <20230605115143.i3squdbqmqebu5ue@quack3> CC: , , From: "yebin (H)" Message-ID: <647DEC75.7080300@huawei.com> Date: Mon, 5 Jun 2023 22:08:53 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: <20230605115143.i3squdbqmqebu5ue@quack3> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.178.185] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To canpemm500010.china.huawei.com (7.192.105.118) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/6/5 19:51, Jan Kara wrote: > On Sat 03-06-23 14:14:11, yebin (H) wrote: >> >> On 2023/5/30 17:57, Jan Kara wrote: >>> On Sat 27-05-23 09:40:17, Ye Bin wrote: >>>> Syzbot found the following issue: >>>> Unable to handle kernel paging request at virtual address dfff800000000005 >>>> KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f] >>> ... >>>> CPU: 0 PID: 6080 Comm: syz-executor747 Not tainted 6.3.0-rc7-syzkaller-g14f8db1c0f9a #0 >>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023 >>>> pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) >>>> pc : ext4_acquire_dquot+0x1d4/0x398 fs/ext4/super.c:6766 >>>> lr : dquot_to_inode fs/ext4/super.c:6740 [inline] >>>> lr : ext4_acquire_dquot+0x1ac/0x398 fs/ext4/super.c:6766 >>> OK, this is bad... >>> >>>> Above issue may happens as follows: >>>> ProcessA ProcessB ProcessC >>>> sys_fsconfig >>>> vfs_fsconfig_locked >>>> reconfigure_super >>>> ext4_remount >>>> dquot_suspend -> suspend all type quota >>>> >>>> sys_fsconfig >>>> vfs_fsconfig_locked >>>> reconfigure_super >>>> ext4_remount >>>> dquot_resume >>>> ret = dquot_load_quota_sb >>>> add_dquot_ref >>>> do_open -> open file O_RDWR >>>> vfs_open >>>> do_dentry_open >>>> get_write_access >>>> atomic_inc_unless_negative(&inode->i_writecount) >>>> ext4_file_open >>>> dquot_file_open >>>> dquot_initialize >>>> __dquot_initialize >>>> dqget >>>> if (!test_bit(DQ_ACTIVE_B, &dquot->dq_flags)) >>>> >>>> __dquot_initialize >>>> __dquot_initialize >>>> dqget >>>> if (!test_bit(DQ_ACTIVE_B, &dquot->dq_flags)) >>>> ext4_acquire_dquot -> Return error >>>> if (ret < 0) >>>> vfs_cleanup_quota_inode >>>> dqopt->files[type] = NULL; >>> But I don't see how this can happen. The code in dquot_load_quota_sb() >>> looks like: >>> >>> error = add_dquot_ref(sb, type); >>> if (error) >>> dquot_disable(sb, type, flags); >>> >>> So if an error happens in add_dquot_ref(), we'll call dquot_disable(). >>> dquot_disable() then does: >>> >>> drop_dquot_ref(sb, cnt); >>> invalidate_dquots(sb, cnt); >>> >>> and invalidate_dquots() waits for reference count of all dquots to drop to >>> 0. Hence if dqget() returned a dquot pointer to ProcessC, then ProcessB >>> should wait until ProcessC drops the dquot reference (hence >>> ext4_acquire_dquot() is done). >>> >>> What am I missing? >>> >>> Honza >> My reproduction condition is: >> mkfs.ext4 -F /dev/sda >> tune2fs -Q usrquota /dev/sda >> >> dquot_disable >> ... >> if ((flags & DQUOT_USAGE_ENABLED && !(flags & >> DQUOT_LIMITS_ENABLED)) >> || (flags & DQUOT_SUSPENDED && flags & (DQUOT_LIMITS_ENABLED | >> DQUOT_USAGE_ENABLED))) >> return -EINVAL; >> ... >> If without enable DQUOT_LIMITS_ENABLED dquot_disable() will just return >> -EINVAL. > Aha, that is the bug! Does attached patch fix your problem? > > Honza Yes , it's works.