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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 97731C43603 for ; Thu, 19 Dec 2019 18:39:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5F61120716 for ; Thu, 19 Dec 2019 18:39:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576780770; bh=uvsaijxYpRjyoi0SSPDf3V+k4x8A1Zu1hj/7bXUk2MQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=h5ynDJSRvlT0LdO880f6x4RciJvRfgQHfLVSO6RWvkGtoSdJh6JVrcQ0leNKbod49 IQ2zEVkaoqUqn0OQe92NvyNf/kO73k2WpcE2rH6nDs41mT0BaN1fdEh+4YGJlTUeCD h5odYq8NfnjGuEqrkaArg/C1OnOJz9hQWeWK3oCw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728219AbfLSSj3 (ORCPT ); Thu, 19 Dec 2019 13:39:29 -0500 Received: from mail.kernel.org ([198.145.29.99]:57638 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728208AbfLSSjY (ORCPT ); Thu, 19 Dec 2019 13:39:24 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2BEA524680; Thu, 19 Dec 2019 18:39:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576780763; bh=uvsaijxYpRjyoi0SSPDf3V+k4x8A1Zu1hj/7bXUk2MQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ut3DddeGrTH3oGLvXklTrRgMIYzMenvv7c7PmapRzuoQWu5xhptS6f7OMqGUz0FGC Kmejrgy4HURuR8yI0yovZY4jewi4uim1/4c1Bn6nKAGhe0BV2QAlzOSkGFMbxeRop4 6I60isxVK055xntMFtkmSbzn3Ukelq6Ie+XW1EsA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tejun Heo , "Williams, Gerald S" , NeilBrown Subject: [PATCH 4.4 106/162] workqueue: Fix pwq ref leak in rescuer_thread() Date: Thu, 19 Dec 2019 19:33:34 +0100 Message-Id: <20191219183214.208412906@linuxfoundation.org> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20191219183150.477687052@linuxfoundation.org> References: <20191219183150.477687052@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Tejun Heo commit e66b39af00f426b3356b96433d620cb3367ba1ff upstream. 008847f66c3 ("workqueue: allow rescuer thread to do more work.") made the rescuer worker requeue the pwq immediately if there may be more work items which need rescuing instead of waiting for the next mayday timer expiration. Unfortunately, it doesn't check whether the pwq is already on the mayday list and unconditionally gets the ref and moves it onto the list. This doesn't corrupt the list but creates an additional reference to the pwq. It got queued twice but will only be removed once. This leak later can trigger pwq refcnt warning on workqueue destruction and prevent freeing of the workqueue. Signed-off-by: Tejun Heo Cc: "Williams, Gerald S" Cc: NeilBrown Cc: stable@vger.kernel.org # v3.19+ Signed-off-by: Greg Kroah-Hartman --- kernel/workqueue.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -2308,8 +2308,14 @@ repeat: */ if (need_to_create_worker(pool)) { spin_lock(&wq_mayday_lock); - get_pwq(pwq); - list_move_tail(&pwq->mayday_node, &wq->maydays); + /* + * Queue iff we aren't racing destruction + * and somebody else hasn't queued it already. + */ + if (wq->rescuer && list_empty(&pwq->mayday_node)) { + get_pwq(pwq); + list_add_tail(&pwq->mayday_node, &wq->maydays); + } spin_unlock(&wq_mayday_lock); } } @@ -4276,7 +4282,8 @@ static void show_pwq(struct pool_workque pr_info(" pwq %d:", pool->id); pr_cont_pool_info(pool); - pr_cont(" active=%d/%d%s\n", pwq->nr_active, pwq->max_active, + pr_cont(" active=%d/%d refcnt=%d%s\n", + pwq->nr_active, pwq->max_active, pwq->refcnt, !list_empty(&pwq->mayday_node) ? " MAYDAY" : ""); hash_for_each(pool->busy_hash, bkt, worker, hentry) {