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 E9D84C433EF for ; Mon, 28 Feb 2022 17:28:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232269AbiB1R3X (ORCPT ); Mon, 28 Feb 2022 12:29:23 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45222 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237120AbiB1R2F (ORCPT ); Mon, 28 Feb 2022 12:28:05 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E2061E5B; Mon, 28 Feb 2022 09:27:21 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 9E2BAB815B3; Mon, 28 Feb 2022 17:27:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 00D79C340F1; Mon, 28 Feb 2022 17:27:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1646069239; bh=CidzmvAFVi43hMNxzqnk5tG9HKIHJRZgVsRGz6ocuw8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Co6JB92vrzGgpBSnV/1W1F6NLD+e+lQPiDQ0i2PiD4cN2gYs0elC1jxyHkY+jUPJu 0ySLr5b+7R/kbW4R1MB6n+y2Oqxw5FTvXkVD7raeE8END+fHulVyXl2ZHowfUXpqhB 3OC+DwqpAlr8jHG5QijfcI54Vl6LpQPmIVcNuN9Y= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, ChenXiaoSong , Laibin Qiu , Christoph Hellwig , Sasha Levin Subject: [PATCH 4.14 14/31] configfs: fix a race in configfs_{,un}register_subsystem() Date: Mon, 28 Feb 2022 18:24:10 +0100 Message-Id: <20220228172201.258455438@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220228172159.515152296@linuxfoundation.org> References: <20220228172159.515152296@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: ChenXiaoSong [ Upstream commit 84ec758fb2daa236026506868c8796b0500c047d ] 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 Signed-off-by: Christoph Hellwig Signed-off-by: Sasha Levin --- fs/configfs/dir.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c index c875f246cb0e9..ccb49caed502c 100644 --- a/fs/configfs/dir.c +++ b/fs/configfs/dir.c @@ -50,6 +50,14 @@ DECLARE_RWSEM(configfs_rename_sem); */ 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) { @@ -1937,7 +1945,9 @@ 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); @@ -1962,7 +1972,9 @@ 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); @@ -2008,7 +2020,9 @@ 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(); } -- 2.34.1