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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 73F9EC3A59E for ; Thu, 22 Aug 2019 02:13:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4E161216F4 for ; Thu, 22 Aug 2019 02:13:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730852AbfHVCNS (ORCPT ); Wed, 21 Aug 2019 22:13:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53226 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727874AbfHVCNS (ORCPT ); Wed, 21 Aug 2019 22:13:18 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 863713DE02; Thu, 22 Aug 2019 02:13:17 +0000 (UTC) Received: from [10.72.12.68] (ovpn-12-68.pek2.redhat.com [10.72.12.68]) by smtp.corp.redhat.com (Postfix) with ESMTP id 73B0F5C228; Thu, 22 Aug 2019 02:13:14 +0000 (UTC) Subject: Re: [PATCH v3] tun: fix use-after-free when register netdev failed From: Jason Wang To: David Miller , yangyingliang@huawei.com Cc: netdev@vger.kernel.org, eric.dumazet@gmail.com, xiyou.wangcong@gmail.com, weiyongjun1@huawei.com References: <1566221479-16094-1-git-send-email-yangyingliang@huawei.com> <20190819.182522.414877916903078544.davem@davemloft.net> Message-ID: Date: Thu, 22 Aug 2019 10:13:11 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Thu, 22 Aug 2019 02:13:17 +0000 (UTC) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 2019/8/20 上午10:28, Jason Wang wrote: > > On 2019/8/20 上午9:25, David Miller wrote: >> From: Yang Yingliang >> Date: Mon, 19 Aug 2019 21:31:19 +0800 >> >>> Call tun_attach() after register_netdevice() to make sure tfile->tun >>> is not published until the netdevice is registered. So the read/write >>> thread can not use the tun pointer that may freed by free_netdev(). >>> (The tun and dev pointer are allocated by alloc_netdev_mqs(), they can >>> be freed by netdev_freemem().) >> register_netdevice() must always be the last operation in the order of >> network device setup. >> >> At the point register_netdevice() is called, the device is visible >> globally >> and therefore all of it's software state must be fully initialized and >> ready for us. >> >> You're going to have to find another solution to these problems. > > > The device is loosely coupled with sockets/queues. Each side is > allowed to be go away without caring the other side. So in this case, > there's a small window that network stack think the device has one > queue but actually not, the code can then safely drop them. Maybe it's > ok here with some comments? > > Or if not, we can try to hold the device before tun_attach and drop it > after register_netdevice(). Hi Yang: I think maybe we can try to hold refcnt instead of playing real num queues here. Do you want to post a V4? Thanks > > Thanks >