netdev - Re: [PATCH v1 net 8/8] mptcp: Use sk_dst_dev_rcu() in mptcp_active

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Message-ID: <e38edeb6-ef11-4dc9-b768-4ac90ee524ab@kernel.org>
Date: Thu, 11 Sep 2025 18:59:43 +0200
From: Matthieu Baerts <matttbe@...nel.org>
To: Kuniyuki Iwashima <kuniyu@...gle.com>
Cc: Simon Horman <horms@...nel.org>, Kuniyuki Iwashima <kuni1840@...il.com>,
 netdev@...r.kernel.org, Mat Martineau <martineau@...nel.org>,
 Geliang Tang <geliang@...nel.org>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH v1 net 8/8] mptcp: Use sk_dst_dev_rcu() in
 mptcp_active_enable().

On 11/09/2025 18:58, Kuniyuki Iwashima wrote:
> On Thu, Sep 11, 2025 at 1:48 AM Matthieu Baerts <matttbe@...nel.org> wrote:
>>
>> Hi Kuniyuki,
>>
>> On 11/09/2025 05:05, Kuniyuki Iwashima wrote:
>>> mptcp_active_enable() is called from subflow_finish_connect(),
>>> which is icsk->icsk_af_ops->sk_rx_dst_set() and it's not always
>>> under RCU.
>>>
>>> Using sk_dst_get(sk)->dev could trigger UAF.
>>>
>>> Also, mptcp_active_enable() forgot dst_release().
>>
>> Oops! Good catch!
>>
>>> Let's use sk_dst_dev_rcu().
>>
>> Thank you! The patch looks good to me, but I also read Eric's replies.
>>
>> If the patches are sent to net-next, will they still have the 'Fixes'
>> tag? If not (but I guess they will), could we have at least have a
>> dedicated patch to add the missing 'dst_release()' please?
> 
> Sure, I'll split the patch into two and keep Fixes: for the
> dst_release() one.

Great, thank you!

Cheers,
Matt
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