netdev - Re: [PATCH v2 net-next 7/7] mptcp: Use __sk_dst_get() and dst_dev_rcu() in mptcp_active

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Message-ID: <CANn89i+ExT8U3bEK=2tKM0TSdo68U-5FbmZzchwiPJVVrjYMkA@mail.gmail.com>
Date: Wed, 17 Sep 2025 07:10:46 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: Kuniyuki Iwashima <kuniyu@...gle.com>
Cc: "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org, 
	Matthieu Baerts <matttbe@...nel.org>, Mat Martineau <martineau@...nel.org>, 
	Geliang Tang <geliang@...nel.org>
Subject: Re: [PATCH v2 net-next 7/7] mptcp: Use __sk_dst_get() and
 dst_dev_rcu() in mptcp_active_enable().

On Tue, Sep 16, 2025 at 2:48 PM Kuniyuki Iwashima <kuniyu@...gle.com> 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.
>
> Let's use __sk_dst_get() and dst_dev_rcu().
>
> Fixes: 27069e7cb3d1 ("mptcp: disable active MPTCP in case of blackhole")
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...gle.com>
> ---

Reviewed-by: Eric Dumazet <edumazet@...gle.com>