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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 915CFC43603 for ; Thu, 5 Dec 2019 11:01:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 51E4524648 for ; Thu, 5 Dec 2019 11:01:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729351AbfLELBO (ORCPT ); Thu, 5 Dec 2019 06:01:14 -0500 Received: from www262.sakura.ne.jp ([202.181.97.72]:53793 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728735AbfLELBN (ORCPT ); Thu, 5 Dec 2019 06:01:13 -0500 Received: from fsav109.sakura.ne.jp (fsav109.sakura.ne.jp [27.133.134.236]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id xB5B0ZXE069614; Thu, 5 Dec 2019 20:00:35 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav109.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav109.sakura.ne.jp); Thu, 05 Dec 2019 20:00:35 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav109.sakura.ne.jp) Received: from [192.168.1.9] (softbank126040062084.bbtec.net [126.40.62.84]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id xB5B0Zfm069611 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NO); Thu, 5 Dec 2019 20:00:35 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: unregister_netdevice: waiting for DEV to become free (2) To: =?UTF-8?Q?Jouni_H=c3=b6gander?= Cc: syzbot , YueHaibing , Julian Anastasov , ddstreet@ieee.org, dvyukov@google.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, syzkaller-bugs@googlegroups.com, Hulk Robot , "David S. Miller" , Lukas Bulwahn References: <0000000000007d22100573d66078@google.com> <87y2vrgkij.fsf@unikie.com> From: Tetsuo Handa Message-ID: Date: Thu, 5 Dec 2019 20:00:35 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.9.1 MIME-Version: 1.0 In-Reply-To: <87y2vrgkij.fsf@unikie.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019/12/05 19:00, Jouni Högander wrote: >> diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c >> index ae3bcb1540ec..562d06c274aa 100644 >> --- a/net/core/net-sysfs.c >> +++ b/net/core/net-sysfs.c >> @@ -1459,14 +1459,14 @@ static int netdev_queue_add_kobject(struct net_device *dev, int index) >> struct kobject *kobj = &queue->kobj; >> int error = 0; >> >> + dev_hold(queue->dev); >> + >> kobj->kset = dev->queues_kset; >> error = kobject_init_and_add(kobj, &netdev_queue_ktype, NULL, >> "tx-%u", index); >> if (error) >> goto err; >> >> - dev_hold(queue->dev); >> - >> #ifdef CONFIG_BQL >> error = sysfs_create_group(kobj, &dql_group); >> if (error) > > Now after reproducing the issue I think this is actually proper fix for > the issue. It's not related to missing error handling in in > tun_set_real_num_queues as I commented earlier. Can you prepare patch > for this? You can write the patch; I don't know about commit a3e23f719f5c4a38 ("net-sysfs: call dev_hold if kobject_init_and_add success"). I was wondering how can the caller tell whether to drop the refcount, for the caller won't be able to know which one (kobject_init_and_add() or sysfs_create_group()) returned an error. Therefore, always taking the refcount seems to be a proper fix...