Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7AA1CC433F5 for ; Thu, 18 Nov 2021 01:46:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5A0F661B1B for ; Thu, 18 Nov 2021 01:46:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242353AbhKRBt3 (ORCPT ); Wed, 17 Nov 2021 20:49:29 -0500 Received: from szxga01-in.huawei.com ([45.249.212.187]:14951 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239516AbhKRBt1 (ORCPT ); Wed, 17 Nov 2021 20:49:27 -0500 Received: from dggeml757-chm.china.huawei.com (unknown [172.30.72.56]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4HvjJJ55DHzZd6c; Thu, 18 Nov 2021 09:44:00 +0800 (CST) Received: from [10.174.179.200] (10.174.179.200) by dggeml757-chm.china.huawei.com (10.1.199.137) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2308.20; Thu, 18 Nov 2021 09:46:24 +0800 Subject: Re: [PATCH net v2] net: vlan: fix a UAF in vlan_dev_real_dev() To: Petr Machata , Jakub Kicinski CC: , , , References: <20211102021218.955277-1-william.xuanziyang@huawei.com> <87k0h9bb9x.fsf@nvidia.com> <20211115094940.138d86dc@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> <87a6i3t2zg.fsf@nvidia.com> From: "Ziyang Xuan (William)" Message-ID: <7f7cbbec-8c4e-a2dc-787b-570d1049a6b4@huawei.com> Date: Thu, 18 Nov 2021 09:46:24 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <87a6i3t2zg.fsf@nvidia.com> Content-Type: text/plain; charset="gbk" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.179.200] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggeml757-chm.china.huawei.com (10.1.199.137) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > Jakub Kicinski writes: > >> On Mon, 15 Nov 2021 18:04:42 +0100 Petr Machata wrote: >>> Ziyang Xuan writes: >>> >>>> diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c >>>> index 55275ef9a31a..a3a0a5e994f5 100644 >>>> --- a/net/8021q/vlan.c >>>> +++ b/net/8021q/vlan.c >>>> @@ -123,9 +123,6 @@ void unregister_vlan_dev(struct net_device *dev, struct list_head *head) >>>> } >>>> >>>> vlan_vid_del(real_dev, vlan->vlan_proto, vlan_id); >>>> - >>>> - /* Get rid of the vlan's reference to real_dev */ >>>> - dev_put(real_dev); >>>> } >>>> >>>> int vlan_check_real_dev(struct net_device *real_dev, >>>> diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c >>>> index 0c21d1fec852..aeeb5f90417b 100644 >>>> --- a/net/8021q/vlan_dev.c >>>> +++ b/net/8021q/vlan_dev.c >>>> @@ -843,6 +843,9 @@ static void vlan_dev_free(struct net_device *dev) >>>> >>>> free_percpu(vlan->vlan_pcpu_stats); >>>> vlan->vlan_pcpu_stats = NULL; >>>> + >>>> + /* Get rid of the vlan's reference to real_dev */ >>>> + dev_put(vlan->real_dev); >>>> } >>>> >>>> void vlan_setup(struct net_device *dev) >>> >>> This is causing reference counting issues when vetoing is involved. >>> Consider the following snippet: >>> >>> ip link add name bond1 type bond mode 802.3ad >>> ip link set dev swp1 master bond1 >>> ip link add name bond1.100 link bond1 type vlan protocol 802.1ad id 100 >>> # ^ vetoed, no netdevice created >>> ip link del dev bond1 >>> >>> The setup process goes like this: vlan_newlink() calls >>> register_vlan_dev() calls netdev_upper_dev_link() calls >>> __netdev_upper_dev_link(), which issues a notifier >>> NETDEV_PRECHANGEUPPER, which yields a non-zero error, >>> because a listener vetoed it. >>> >>> So it unwinds, skipping dev_hold(real_dev), but eventually the VLAN ends >>> up decreasing reference count of the real_dev. Then when when the bond >>> netdevice is removed, we get an endless loop of: >>> >>> kernel:unregister_netdevice: waiting for bond1 to become free. Usage count = 0 >>> >>> Moving the dev_hold(real_dev) to always happen even if the >>> netdev_upper_dev_link() call makes the issue go away. >> >> I think we should move the dev_hold() to ndo_init(), otherwise >> it's hard to reason if destructor was invoked or not if >> register_netdevice() errors out. > > Ziyang Xuan, do you intend to take care of this? > . I am reading the related processes according to the problem scenario. And I will give a more clear sequence and root cause as soon as possible by some necessary tests. Thank you!