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=-7.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no 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 83BACC433E3 for ; Sat, 25 Jul 2020 00:02:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6B1302070B for ; Sat, 25 Jul 2020 00:02:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726769AbgGYACV (ORCPT ); Fri, 24 Jul 2020 20:02:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52180 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726572AbgGYACV (ORCPT ); Fri, 24 Jul 2020 20:02:21 -0400 Received: from shards.monkeyblade.net (shards.monkeyblade.net [IPv6:2620:137:e000::1:9]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3ECE5C0619D3; Fri, 24 Jul 2020 17:02:21 -0700 (PDT) Received: from localhost (unknown [IPv6:2601:601:9f00:477::3d5]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id 961C612756FEE; Fri, 24 Jul 2020 16:45:35 -0700 (PDT) Date: Fri, 24 Jul 2020 17:02:20 -0700 (PDT) Message-Id: <20200724.170220.1275270219725381485.davem@davemloft.net> To: andrea.righi@canonical.com Cc: boris.ostrovsky@oracle.com, jgross@suse.com, sstabellini@kernel.org, kuba@kernel.org, xen-devel@lists.xenproject.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] xen-netfront: fix potential deadlock in xennet_remove() From: David Miller In-Reply-To: <20200724085910.GA1043801@xps-13> References: <20200724085910.GA1043801@xps-13> X-Mailer: Mew version 6.8 on Emacs 26.3 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Fri, 24 Jul 2020 16:45:35 -0700 (PDT) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Andrea Righi Date: Fri, 24 Jul 2020 10:59:10 +0200 > 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 > --- > Changes in v2: > - remove all dev_dbg() calls (as suggested by David Miller) Applied, thank you.