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 C7AAACCA48E for ; Mon, 13 Jun 2022 10:31:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346551AbiFMKa6 (ORCPT ); Mon, 13 Jun 2022 06:30:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34994 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344563AbiFMK3C (ORCPT ); Mon, 13 Jun 2022 06:29:02 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EA708255B7; Mon, 13 Jun 2022 03:20:25 -0700 (PDT) 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 dfw.source.kernel.org (Postfix) with ESMTPS id 33D6360B91; Mon, 13 Jun 2022 10:20:25 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3FDA1C34114; Mon, 13 Jun 2022 10:20:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1655115624; bh=g7SB3apUoO7P6BCpj7sZDzJFWpEJqgCZHd9WtGuebqQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=sLKdtxfa/+kzBF9eggOVSZzkRs+GU3O2XCALuXYm7OgrMWdszruOZ+yDhs3B4IeHK i5mXmnah57kLmF5ZKKrYZmamX6UkLiSz4iYv+ib0RL2QIy0fgRbIbSmsfApComBQeo Eoy6UPIcJRy/eUtieUQxz0YyfbTwhEQmh+SKxaV4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Donald Buczek , Guoqing Jiang , Song Liu , Sasha Levin Subject: [PATCH 4.9 152/167] md: protect md_unregister_thread from reentrancy Date: Mon, 13 Jun 2022 12:10:26 +0200 Message-Id: <20220613094916.572509483@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220613094840.720778945@linuxfoundation.org> References: <20220613094840.720778945@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: Guoqing Jiang [ Upstream commit 1e267742283a4b5a8ca65755c44166be27e9aa0f ] Generally, the md_unregister_thread is called with reconfig_mutex, but raid_message in dm-raid doesn't hold reconfig_mutex to unregister thread, so md_unregister_thread can be called simulitaneously from two call sites in theory. Then after previous commit which remove the protection of reconfig_mutex for md_unregister_thread completely, the potential issue could be worse than before. Let's take pers_lock at the beginning of function to ensure reentrancy. Reported-by: Donald Buczek Signed-off-by: Guoqing Jiang Signed-off-by: Song Liu Signed-off-by: Sasha Levin --- drivers/md/md.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index 0197d18b5407..9e8373e7e287 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -7254,17 +7254,22 @@ EXPORT_SYMBOL(md_register_thread); void md_unregister_thread(struct md_thread **threadp) { - struct md_thread *thread = *threadp; - if (!thread) - return; - pr_debug("interrupting MD-thread pid %d\n", task_pid_nr(thread->tsk)); - /* Locking ensures that mddev_unlock does not wake_up a + struct md_thread *thread; + + /* + * Locking ensures that mddev_unlock does not wake_up a * non-existent thread */ spin_lock(&pers_lock); + thread = *threadp; + if (!thread) { + spin_unlock(&pers_lock); + return; + } *threadp = NULL; spin_unlock(&pers_lock); + pr_debug("interrupting MD-thread pid %d\n", task_pid_nr(thread->tsk)); kthread_stop(thread->tsk); kfree(thread); } -- 2.35.1