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=ham 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 935C8C43603 for ; Thu, 19 Dec 2019 18:48:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6AE3124676 for ; Thu, 19 Dec 2019 18:48:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576781310; bh=YU3DxByc+F69niV6pf6clyyEWdlANzDaTxDs6Yqk0Ts=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=V1DsTRC3yXQ35f67BMoMzktwXB9qORZxOOB4VlzhKA6VmsN3h8mb1cKIL8UfLUrtp 7t46v9IGAKTwAcKnKVaWev2l39eoi7hBwRRiIz0XW6Lw6TXrXB/NBgl3isBxIP4Utn ezaNQzOQCcutIXEzAbDMZ5UhkXzTkIotTtW4xyj8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729637AbfLSSs3 (ORCPT ); Thu, 19 Dec 2019 13:48:29 -0500 Received: from mail.kernel.org ([198.145.29.99]:41562 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729630AbfLSSs0 (ORCPT ); Thu, 19 Dec 2019 13:48:26 -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 71C5E2465E; Thu, 19 Dec 2019 18:48:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576781305; bh=YU3DxByc+F69niV6pf6clyyEWdlANzDaTxDs6Yqk0Ts=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PpHRFZAaFcPRC9nnxTKv+h0DgjUDStFm1We4z47dw9/Ums07NDMeuXNi9hdwvfLq4 VEfKqIVgf78I0kG0OA8QI8LFUUMZgyRpTFK5t8KqZSorUVTESTvUwCjhQwlvsYp4gb M/ayCYHvTLkhva7MBXfiHsQhGuodAk93shAgej9c= 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 4.9 126/199] workqueue: Fix pwq ref leak in rescuer_thread() Date: Thu, 19 Dec 2019 19:33:28 +0100 Message-Id: <20191219183221.957027353@linuxfoundation.org> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20191219183214.629503389@linuxfoundation.org> References: <20191219183214.629503389@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 @@ -2344,8 +2344,14 @@ 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); } } @@ -4358,7 +4364,8 @@ 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) {