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 1F3F1C433F5 for ; Tue, 15 Feb 2022 06:54:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233178AbiBOGzA (ORCPT ); Tue, 15 Feb 2022 01:55:00 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:45934 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229575AbiBOGy6 (ORCPT ); Tue, 15 Feb 2022 01:54:58 -0500 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C980727B2E for ; Mon, 14 Feb 2022 22:54:45 -0800 (PST) Received: from kwepemi500020.china.huawei.com (unknown [172.30.72.57]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4JyWyV2QFZzbkSj; Tue, 15 Feb 2022 14:53:38 +0800 (CST) Received: from kwepemm600015.china.huawei.com (7.193.23.52) by kwepemi500020.china.huawei.com (7.221.188.8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Tue, 15 Feb 2022 14:54:43 +0800 Received: from huawei.com (10.175.127.227) by kwepemm600015.china.huawei.com (7.193.23.52) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Tue, 15 Feb 2022 14:54:43 +0800 From: ChenXiaoSong To: , CC: , , , , Subject: [PATCH -next] configfs: fix a race in configfs_{,un}register_subsystem() Date: Tue, 15 Feb 2022 15:10:30 +0800 Message-ID: <20220215071030.3067982-1-chenxiaosong2@huawei.com> X-Mailer: git-send-email 2.31.1 MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [10.175.127.227] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To kwepemm600015.china.huawei.com (7.193.23.52) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When configfs_register_subsystem() or configfs_unregister_subsystem() is executing link_group() or unlink_group(), it is possible that two processes add or delete list concurrently. Some unfortunate interleavings of them can cause kernel panic. One of cases is: A --> B --> C --> D A <-- B <-- C <-- D delete list_head *B | delete list_head *C --------------------------------|----------------------------------- configfs_unregister_subsystem | configfs_unregister_subsystem unlink_group | unlink_group unlink_obj | unlink_obj list_del_init | list_del_init __list_del_entry | __list_del_entry __list_del | __list_del // next == C | next->prev = prev | | next->prev = prev prev->next = next | | // prev == B | prev->next = next Fix this by adding mutex when calling link_group() or unlink_group(), but parent configfs_subsystem is NULL when config_item is root. So I create a mutex configfs_subsystem_mutex. Fixes: 7063fbf22611 ("[PATCH] configfs: User-driven configuration filesystem") Signed-off-by: ChenXiaoSong Signed-off-by: Laibin Qiu --- fs/configfs/dir.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c index 688f28b0c4f8..170538639533 100644 --- a/fs/configfs/dir.c +++ b/fs/configfs/dir.c @@ -35,6 +35,14 @@ */ DEFINE_SPINLOCK(configfs_dirent_lock); +/* + * All of link_obj/unlink_obj/link_group/unlink_group require that + * subsys->su_mutex is held. + * But parent configfs_subsystem is NULL when config_item is root. + * Use this mutex when config_item is root. + */ +static DEFINE_MUTEX(configfs_subsystem_mutex); + static void configfs_d_iput(struct dentry * dentry, struct inode * inode) { @@ -1927,7 +1935,9 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys) group->cg_item.ci_name = group->cg_item.ci_namebuf; sd = root->d_fsdata; + mutex_lock(&configfs_subsystem_mutex); link_group(to_config_group(sd->s_element), group); + mutex_unlock(&configfs_subsystem_mutex); inode_lock_nested(d_inode(root), I_MUTEX_PARENT); @@ -1952,7 +1962,9 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys) inode_unlock(d_inode(root)); if (err) { + mutex_lock(&configfs_subsystem_mutex); unlink_group(group); + mutex_unlock(&configfs_subsystem_mutex); configfs_release_fs(); } put_fragment(frag); @@ -1999,7 +2011,9 @@ void configfs_unregister_subsystem(struct configfs_subsystem *subsys) dput(dentry); + mutex_lock(&configfs_subsystem_mutex); unlink_group(group); + mutex_unlock(&configfs_subsystem_mutex); configfs_release_fs(); } -- 2.31.1