Received-SPF: Pass (protection.outlook.com: domain of nvidia.com designates
 216.228.112.34 as permitted sender) receiver=protection.outlook.com;
 client-ip=216.228.112.34; helo=mail.nvidia.com;
References: <20211102021218.955277-1-william.xuanziyang@huawei.com>
 <87k0h9bb9x.fsf@nvidia.com>
 <20211115094940.138d86dc@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
 <87a6i3t2zg.fsf@nvidia.com>
 <7f7cbbec-8c4e-a2dc-787b-570d1049a6b4@huawei.com>
 <20211118061735.5357f739@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
 <c240e0e0-256c-698b-4a98-47490869faa3@huawei.com>
 <8735nstq62.fsf@nvidia.com>
 <daae2fe3-997c-a390-afae-15ff33ba3d1c@huawei.com>
 <87k0gzrqw8.fsf@nvidia.com>
User-agent: mu4e 1.4.15; emacs 27.2
From:   Petr Machata <petrm@nvidia.com>
To:     Petr Machata <petrm@nvidia.com>
CC:     "Ziyang Xuan (William)" <william.xuanziyang@huawei.com>,
        Jakub Kicinski <kuba@kernel.org>, <davem@davemloft.net>,
        <jgg@nvidia.com>, <netdev@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH net v2] net: vlan: fix a UAF in vlan_dev_real_dev()
In-Reply-To: <87k0gzrqw8.fsf@nvidia.com>
Date:   Thu, 25 Nov 2021 12:33:11 +0100
Message-ID: <87v90gqxl4.fsf@nvidia.com>
MIME-Version: 1.0
Content-Type: text/plain
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 25 Nov 2021 11:33:15.5151
 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: 2563e9c6-2843-4270-f577-08d9b0075f17
X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a
X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.112.34];Helo=[mail.nvidia.com]
X-MS-Exchange-CrossTenant-AuthSource: CO1NAM11FT015.eop-nam11.prod.protection.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Anonymous
X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem
X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR12MB5587
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org


Petr Machata <petrm@nvidia.com> writes:

> Ziyang Xuan (William) <william.xuanziyang@huawei.com> writes:
>
>>> 
>>> Ziyang Xuan (William) <william.xuanziyang@huawei.com> writes:
>>> 
>>>> I need some time to test my some ideas. And anyone has good ideas, please
>>>> do not be stingy.
>>> 
>>> Jakub Kicinski <kuba@kernel.org> writes:
>>> 
>>>> 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.
>>> 
>>> That makes sense to me. We always put real_dev in the destructor, so we
>>> should always hold it in the constructor...
>>
>> Inject error before dev_hold(real_dev) in register_vlan_dev(), and execute
>> the following testcase:
>>
>> ip link add dev dummy1 type dummy
>> ip link add name dummy1.100 link dummy1 type vlan id 100 // failed for error injection
>> ip link del dev dummy1
>>
>> Make the problem repro. The problem is solved using the following fix
>> according to the Jakub's suggestion:
>>
>> diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c
>> index a3a0a5e994f5..abaa5d96ded2 100644
>> --- a/net/8021q/vlan.c
>> +++ b/net/8021q/vlan.c
>> @@ -184,9 +184,6 @@ int register_vlan_dev(struct net_device *dev, struct netlink_ext_ack *extack)
>>         if (err)
>>                 goto out_unregister_netdev;
>>
>> -       /* Account for reference in struct vlan_dev_priv */
>> -       dev_hold(real_dev);
>> -
>>         vlan_stacked_transfer_operstate(real_dev, dev, vlan);
>>         linkwatch_fire_event(dev); /* _MUST_ call rfc2863_policy() */
>>
>> diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
>> index ab6dee28536d..a54535cbcf4c 100644
>> --- a/net/8021q/vlan_dev.c
>> +++ b/net/8021q/vlan_dev.c
>> @@ -615,6 +615,9 @@ static int vlan_dev_init(struct net_device *dev)
>>         if (!vlan->vlan_pcpu_stats)
>>                 return -ENOMEM;
>>
>> +       /* Get vlan's reference to real_dev */
>> +       dev_hold(real_dev);
>>
>>
>> If there is not any other idea and objection, I will send the fix patch later.
>>
>> Thank you!
>
> This fixes the issue in my repro, and does not seems to break anything.
> We'll take it to full regression overnight, I'll report back tomorrow
> about the result.

Sorry, was AFK yesterday. It does look good.