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 39180C4363D for ; Mon, 27 Jul 2020 23:27:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1776C208E4 for ; Mon, 27 Jul 2020 23:27:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595892439; bh=U+chRqPGR8rJrwHBA7q6Oj2Gm8e0BLsd3/ugWeyaAfw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=UdxpLrDBvPCWiR466j+Pg2Is2A/vZVxcyURmoFglcjVC7eG9GfYJFdnQZvpqkEB1K 7inIovmvoC3MrXAlQbZ+MRUUrclOR5jxdrPRB7rUsklIML/Qu+u69zeWwebK2CJeQR wrffRJ9i1TVKaHZagYXKDuHPKBIhkhNTrY/CQf8U= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728437AbgG0X1Q (ORCPT ); Mon, 27 Jul 2020 19:27:16 -0400 Received: from mail.kernel.org ([198.145.29.99]:36204 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728416AbgG0XY6 (ORCPT ); Mon, 27 Jul 2020 19:24:58 -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 91BF8208E4; Mon, 27 Jul 2020 23:24:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595892297; bh=U+chRqPGR8rJrwHBA7q6Oj2Gm8e0BLsd3/ugWeyaAfw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=aS9gm9q4YI0vvOm1tahQfiVySX+ojIgDSCMi/Ps3Y3MfwKdOSXRIMeZQFV+DyHLkM j8AxaqcvwXpv6C83Nz8W2pGQTXHsFVjHRehksxxWZt2BNFUnMk3UPyECnb0dXgETzM xa2vSqTx5xlfqyAQKiDtydLidOpXcDLMN5C0mQ34= 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 4.19 10/10] xen-netfront: fix potential deadlock in xennet_remove() Date: Mon, 27 Jul 2020 19:24:43 -0400 Message-Id: <20200727232443.718000-10-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200727232443.718000-1-sashal@kernel.org> References: <20200727232443.718000-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@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 6b4675a9494b2..c8e84276e6397 100644 --- a/drivers/net/xen-netfront.c +++ b/drivers/net/xen-netfront.c @@ -63,6 +63,8 @@ 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 { @@ -1337,12 +1339,15 @@ 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: @@ -2142,28 +2147,43 @@ 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