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

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Message-ID: <CAAVpQUAvDQdodvheTKmRE6HiaBLHELpyc3jfbHPvxFiJ7jE9mg@mail.gmail.com>
Date: Thu, 11 Sep 2025 09:58:33 -0700
From: Kuniyuki Iwashima <kuniyu@...gle.com>
To: Matthieu Baerts <matttbe@...nel.org>
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 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.