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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 85D4AC11F66 for ; Tue, 29 Jun 2021 14:27:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6CE3261DB4 for ; Tue, 29 Jun 2021 14:27:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234438AbhF2OaG (ORCPT ); Tue, 29 Jun 2021 10:30:06 -0400 Received: from szxga01-in.huawei.com ([45.249.212.187]:6023 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233941AbhF2O3x (ORCPT ); Tue, 29 Jun 2021 10:29:53 -0400 Received: from dggeme754-chm.china.huawei.com (unknown [172.30.72.55]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4GDmrY1gLvzXmVb; Tue, 29 Jun 2021 22:22:05 +0800 (CST) Received: from huawei.com (10.175.127.227) by dggeme754-chm.china.huawei.com (10.3.19.100) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2; Tue, 29 Jun 2021 22:27:23 +0800 From: Ye Bin To: , , , , CC: Ye Bin Subject: [PATCH 2/2] ext4: Fix potential uas-after-free about sbi->s_mmp_tsk when kmmpd kthread exit before set sbi->s_mmp_tsk Date: Tue, 29 Jun 2021 22:36:03 +0800 Message-ID: <20210629143603.2166962-3-yebin10@huawei.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210629143603.2166962-1-yebin10@huawei.com> References: <20210629143603.2166962-1-yebin10@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [10.175.127.227] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggeme754-chm.china.huawei.com (10.3.19.100) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Now sbi->s_mmp_tsk is created with kthread_run, then kmmpd maybe already running and even exit as exception. Even though we set sbi->s_mmp_tsk with NULL before kmmpd kthread exit, but "sbi->s_mmp_tsk=kthread_run(XX)" may set after set with NULL. mount kmmpd | | |-call kthread_run | | |-kmmpd runing | |-kmmpd exit sbi->s_mmp_tsk=NULL | | |-kthread_run return | | and set sbi->s_mmp_tsk | | | |-then we get wild ptr"sbi->s_mmp_tsk" and later trigger UAF This patch is base on previous "ext4: Fix use-after-free about sbi->s_mmp_tsk". Previous patch ensure kmmpd kthread exit by itself will set sbi->s_mmp_tsk with NULL. We can create kthread first, and then wakeup kmmpd kthread later. Signed-off-by: Ye Bin --- fs/ext4/mmp.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c index fc18a8c205c7..6ec1ea182cc0 100644 --- a/fs/ext4/mmp.c +++ b/fs/ext4/mmp.c @@ -394,16 +394,18 @@ int ext4_multi_mount_protect(struct super_block *sb, /* * Start a kernel thread to update the MMP block periodically. */ - EXT4_SB(sb)->s_mmp_tsk = kthread_run(kmmpd, sb, "kmmpd-%.*s", - (int)sizeof(mmp->mmp_bdevname), - bdevname(bh->b_bdev, - mmp->mmp_bdevname)); + EXT4_SB(sb)->s_mmp_tsk = kthread_create(kmmpd, sb, "kmmpd-%.*s", + (int)sizeof(mmp->mmp_bdevname), + bdevname(bh->b_bdev, + mmp->mmp_bdevname)); + if (IS_ERR(EXT4_SB(sb)->s_mmp_tsk)) { EXT4_SB(sb)->s_mmp_tsk = NULL; ext4_warning(sb, "Unable to create kmmpd thread for %s.", sb->s_id); goto failed; } + wake_up_process(EXT4_SB(sb)->s_mmp_tsk); return 0; -- 2.31.1