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=-13.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,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 18805C433EA for ; Mon, 27 Jul 2020 23:26:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E8A1B20786 for ; Mon, 27 Jul 2020 23:26:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595892365; bh=5A5lx/WYgPnL2PcAsnUTD1sCwUsJ/qCAZDKh9yMqyfc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=MmzutiU8SElApk6IAMoThLreica2mAp1CrA1n+Y+SpB66QVcRw8SniqeodnDwVsMO 8/47fCkFnWsspDgEdVn+BFPamHxOmnDbE8GJ9tr9wQ3zxzb0ESw5PvfBWbZNkN7UCr A8KRu9UnJRRpvIBYnDJ+Vy8EjSo82HGCmIqu8178= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728614AbgG0XZ0 (ORCPT ); Mon, 27 Jul 2020 19:25:26 -0400 Received: from mail.kernel.org ([198.145.29.99]:36750 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728605AbgG0XZZ (ORCPT ); Mon, 27 Jul 2020 19:25:25 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E996D22B40; Mon, 27 Jul 2020 23:25:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595892324; bh=5A5lx/WYgPnL2PcAsnUTD1sCwUsJ/qCAZDKh9yMqyfc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TVlNnCtQw6ltBsOhYsgGUzMptpNAT2vHABaqHnwMYX1idj06mSMdgB3aMXULpdckY HpVt80OY5YOSHfTvmOrCxd3eCU5xA3Mimczxx4dyKT+2f+7m2PZJPEahPspWcl8PAO IqgSSkxS6HfpTrdn8VbCR1aLLlrtyK61GkM4+FvU= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Andrea Righi , "David S . Miller" , Sasha Levin , xen-devel@lists.xenproject.org, netdev@vger.kernel.org Subject: [PATCH AUTOSEL 4.9 7/7] xen-netfront: fix potential deadlock in xennet_remove() Date: Mon, 27 Jul 2020 19:25:14 -0400 Message-Id: <20200727232514.718265-7-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200727232514.718265-1-sashal@kernel.org> References: <20200727232514.718265-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Andrea Righi [ Upstream commit c2c633106453611be07821f53dff9e93a9d1c3f0 ] There's a potential race in xennet_remove(); this is what the driver is doing upon unregistering a network device: 1. state = read bus state 2. if state is not "Closed": 3. request to set state to "Closing" 4. wait for state to be set to "Closing" 5. request to set state to "Closed" 6. wait for state to be set to "Closed" If the state changes to "Closed" immediately after step 1 we are stuck forever in step 4, because the state will never go back from "Closed" to "Closing". Make sure to check also for state == "Closed" in step 4 to prevent the deadlock. Also add a 5 sec timeout any time we wait for the bus state to change, to avoid getting stuck forever in wait_event(). Signed-off-by: Andrea Righi Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- drivers/net/xen-netfront.c | 64 +++++++++++++++++++++++++------------- 1 file changed, 42 insertions(+), 22 deletions(-) diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c index 6d391a268469f..ceaf6b30d683d 100644 --- a/drivers/net/xen-netfront.c +++ b/drivers/net/xen-netfront.c @@ -62,6 +62,8 @@ module_param_named(max_queues, xennet_max_queues, uint, 0644); MODULE_PARM_DESC(max_queues, "Maximum number of queues per virtual interface"); +#define XENNET_TIMEOUT (5 * HZ) + static const struct ethtool_ops xennet_ethtool_ops; struct netfront_cb { @@ -1355,12 +1357,15 @@ static struct net_device *xennet_create_dev(struct xenbus_device *dev) netif_carrier_off(netdev); - xenbus_switch_state(dev, XenbusStateInitialising); - wait_event(module_wq, - xenbus_read_driver_state(dev->otherend) != - XenbusStateClosed && - xenbus_read_driver_state(dev->otherend) != - XenbusStateUnknown); + do { + xenbus_switch_state(dev, XenbusStateInitialising); + err = wait_event_timeout(module_wq, + xenbus_read_driver_state(dev->otherend) != + XenbusStateClosed && + xenbus_read_driver_state(dev->otherend) != + XenbusStateUnknown, XENNET_TIMEOUT); + } while (!err); + return netdev; exit: @@ -2172,28 +2177,43 @@ static const struct attribute_group xennet_dev_group = { }; #endif /* CONFIG_SYSFS */ -static int xennet_remove(struct xenbus_device *dev) +static void xennet_bus_close(struct xenbus_device *dev) { - struct netfront_info *info = dev_get_drvdata(&dev->dev); - - dev_dbg(&dev->dev, "%s\n", dev->nodename); + int ret; - if (xenbus_read_driver_state(dev->otherend) != XenbusStateClosed) { + if (xenbus_read_driver_state(dev->otherend) == XenbusStateClosed) + return; + do { xenbus_switch_state(dev, XenbusStateClosing); - wait_event(module_wq, - xenbus_read_driver_state(dev->otherend) == - XenbusStateClosing || - xenbus_read_driver_state(dev->otherend) == - XenbusStateUnknown); + ret = wait_event_timeout(module_wq, + xenbus_read_driver_state(dev->otherend) == + XenbusStateClosing || + xenbus_read_driver_state(dev->otherend) == + XenbusStateClosed || + xenbus_read_driver_state(dev->otherend) == + XenbusStateUnknown, + XENNET_TIMEOUT); + } while (!ret); + + if (xenbus_read_driver_state(dev->otherend) == XenbusStateClosed) + return; + do { xenbus_switch_state(dev, XenbusStateClosed); - wait_event(module_wq, - xenbus_read_driver_state(dev->otherend) == - XenbusStateClosed || - xenbus_read_driver_state(dev->otherend) == - XenbusStateUnknown); - } + ret = wait_event_timeout(module_wq, + xenbus_read_driver_state(dev->otherend) == + XenbusStateClosed || + xenbus_read_driver_state(dev->otherend) == + XenbusStateUnknown, + XENNET_TIMEOUT); + } while (!ret); +} + +static int xennet_remove(struct xenbus_device *dev) +{ + struct netfront_info *info = dev_get_drvdata(&dev->dev); + xennet_bus_close(dev); xennet_disconnect_backend(info); if (info->netdev->reg_state == NETREG_REGISTERED) -- 2.25.1