netdev - Re: [PATCH net v4] team: fix null-ptr-deref when team device type is changed

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Message-ID: <20250905080010.GA88822@dev-dsk-acsjakub-1b-6f9934e2.eu-west-1.amazon.com>
Date: Fri, 5 Sep 2025 08:00:10 +0000
From: Jakub Acs <acsjakub@...zon.de>
To: Paolo Abeni <pabeni@...hat.com>
CC: "Ziyang Xuan (William)" <william.xuanziyang@...wei.com>,
	<jiri@...nulli.us>, <davem@...emloft.net>, <edumazet@...gle.com>,
	<kuba@...nel.org>, <netdev@...r.kernel.org>, <leon@...nel.org>,
	<ye.xingchen@....com.cn>, <liuhangbin@...il.com>
Subject: Re: [PATCH net v4] team: fix null-ptr-deref when team device type is
 changed

On Wed, Sep 13, 2023 at 08:28:13AM +0200, Paolo Abeni wrote:
> To me both cases look the same in the end: the team driver sets and use
> header_ops of a different device that will assume dev_priv() being a
> different struct.
> 

Hi Paolo, we're seeing syzkaller to run into this exact issue (type
confusion) in ip6gre_header, when adding ip6gre device as a port for a
team device.

> I'm guessing a generic solution could be implementing 'trampoline'
> header_ops that just call into the lower port corresponding op, and
> assigning such ops to the team device every time the lower has non
> ethernet header_ops.
> 
> team_dev_type_check_change() should then probably check both dev->type
> and dev->header_ops.

I tried implementing such trampoline for header_ops.create op for team,
and have the following problem: 
At the time header_ops.create is called on a team device, I don't know
which port device will be used to transmit the skb in the end. 

Could you elaborate what would be the solution for that, please?

Kind Regards,
Jakub

P.S.: Sorry for reviving 2y old thread, but I felt it's better than 
opening a new one since the context is here. Correct me if I'm wrong or
if you'd prefer otherwise, please :)

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