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

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Message-ID: <e4e2a47d-f653-43a3-86ab-f958264449ad@kernel.org>
Date: Thu, 11 Sep 2025 10:48:20 +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().

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?

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.