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,URIBL_BLOCKED,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 27EECC10F14 for ; Thu, 10 Oct 2019 08:53:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F33902064A for ; Thu, 10 Oct 2019 08:53:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570697633; bh=6xA0OjtMQAkM6FlhW2SATp8wTFV1qQGzpiLWe71Hg/Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=qi9urS3K8/lNiMiyQ9m7IbPVE4tILoFyhcmMfLc3xX+KnfzOrvLqeqJT67CpMO+/L CSdsxNzGfRH4RfVlT08yWXvbpRH0+rW86QsQ6POFKDnJW55VkbUPi9XPkEw5f39xdW Ylhg2t2IOmbkdxEvWgc+fpSag9323IS3yKIJBLUI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388278AbfJJIxr (ORCPT ); Thu, 10 Oct 2019 04:53:47 -0400 Received: from mail.kernel.org ([198.145.29.99]:58782 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388950AbfJJIvX (ORCPT ); Thu, 10 Oct 2019 04:51:23 -0400 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 F33012190F; Thu, 10 Oct 2019 08:51:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570697479; bh=6xA0OjtMQAkM6FlhW2SATp8wTFV1qQGzpiLWe71Hg/Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0NbIfEnhUUo7grUWfRZ0f7wp0ksz/hyDhW+QzIdAT/8dnLdDKc+3AhPrR/XsP221y n22WCCbuPZyyteyPDlVD05hDUnHvNffUKfse2wMjj/Py21RCGgjIozKWntJ9aOYWJq 1TEgcagZiXr0ge/DPl58/n9our7XSAorzQjT4qkU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, James Dingwall , Juergen Gross , Boris Ostrovsky Subject: [PATCH 4.14 25/61] xen/xenbus: fix self-deadlock after killing user process Date: Thu, 10 Oct 2019 10:36:50 +0200 Message-Id: <20191010083504.679557065@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191010083449.500442342@linuxfoundation.org> References: <20191010083449.500442342@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Juergen Gross commit a8fabb38525c51a094607768bac3ba46b3f4a9d5 upstream. In case a user process using xenbus has open transactions and is killed e.g. via ctrl-C the following cleanup of the allocated resources might result in a deadlock due to trying to end a transaction in the xenbus worker thread: [ 2551.474706] INFO: task xenbus:37 blocked for more than 120 seconds. [ 2551.492215] Tainted: P OE 5.0.0-29-generic #5 [ 2551.510263] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 2551.528585] xenbus D 0 37 2 0x80000080 [ 2551.528590] Call Trace: [ 2551.528603] __schedule+0x2c0/0x870 [ 2551.528606] ? _cond_resched+0x19/0x40 [ 2551.528632] schedule+0x2c/0x70 [ 2551.528637] xs_talkv+0x1ec/0x2b0 [ 2551.528642] ? wait_woken+0x80/0x80 [ 2551.528645] xs_single+0x53/0x80 [ 2551.528648] xenbus_transaction_end+0x3b/0x70 [ 2551.528651] xenbus_file_free+0x5a/0x160 [ 2551.528654] xenbus_dev_queue_reply+0xc4/0x220 [ 2551.528657] xenbus_thread+0x7de/0x880 [ 2551.528660] ? wait_woken+0x80/0x80 [ 2551.528665] kthread+0x121/0x140 [ 2551.528667] ? xb_read+0x1d0/0x1d0 [ 2551.528670] ? kthread_park+0x90/0x90 [ 2551.528673] ret_from_fork+0x35/0x40 Fix this by doing the cleanup via a workqueue instead. Reported-by: James Dingwall Fixes: fd8aa9095a95c ("xen: optimize xenbus driver for multiple concurrent xenstore accesses") Cc: # 4.11 Signed-off-by: Juergen Gross Reviewed-by: Boris Ostrovsky Signed-off-by: Boris Ostrovsky Signed-off-by: Greg Kroah-Hartman --- drivers/xen/xenbus/xenbus_dev_frontend.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) --- a/drivers/xen/xenbus/xenbus_dev_frontend.c +++ b/drivers/xen/xenbus/xenbus_dev_frontend.c @@ -55,6 +55,7 @@ #include #include #include +#include #include #include @@ -113,6 +114,8 @@ struct xenbus_file_priv { wait_queue_head_t read_waitq; struct kref kref; + + struct work_struct wq; }; /* Read out any raw xenbus messages queued up. */ @@ -297,14 +300,14 @@ static void watch_fired(struct xenbus_wa mutex_unlock(&adap->dev_data->reply_mutex); } -static void xenbus_file_free(struct kref *kref) +static void xenbus_worker(struct work_struct *wq) { struct xenbus_file_priv *u; struct xenbus_transaction_holder *trans, *tmp; struct watch_adapter *watch, *tmp_watch; struct read_buffer *rb, *tmp_rb; - u = container_of(kref, struct xenbus_file_priv, kref); + u = container_of(wq, struct xenbus_file_priv, wq); /* * No need for locking here because there are no other users, @@ -330,6 +333,18 @@ static void xenbus_file_free(struct kref kfree(u); } +static void xenbus_file_free(struct kref *kref) +{ + struct xenbus_file_priv *u; + + /* + * We might be called in xenbus_thread(). + * Use workqueue to avoid deadlock. + */ + u = container_of(kref, struct xenbus_file_priv, kref); + schedule_work(&u->wq); +} + static struct xenbus_transaction_holder *xenbus_get_transaction( struct xenbus_file_priv *u, uint32_t tx_id) { @@ -626,6 +641,7 @@ static int xenbus_file_open(struct inode INIT_LIST_HEAD(&u->watches); INIT_LIST_HEAD(&u->read_buffers); init_waitqueue_head(&u->read_waitq); + INIT_WORK(&u->wq, xenbus_worker); mutex_init(&u->reply_mutex); mutex_init(&u->msgbuffer_mutex);