* Re: [PATCH net] mptcp: fix race condition in mptcp_schedule_work()
[not found] <20251113103924.3737425-1-edumazet@google.com>
@ 2025-11-13 17:35 ` Matthieu Baerts
0 siblings, 0 replies; only message in thread
From: Matthieu Baerts @ 2025-11-13 17:35 UTC (permalink / raw)
To: Eric Dumazet
Cc: Mat Martineau, Geliang Tang, Florian Westphal, netdev,
eric.dumazet, syzbot+355158e7e301548a1424, David S . Miller,
Jakub Kicinski, Paolo Abeni, MPTCP Linux
Hi Eric,
(+cc MPTCP ML)
On 13/11/2025 11:39, Eric Dumazet wrote:
> syzbot reported use-after-free in mptcp_schedule_work() [1]
>
> Issue here is that mptcp_schedule_work() schedules a work,
> then gets a refcount on sk->sk_refcnt if the work was scheduled.
> This refcount will be released by mptcp_worker().
>
> [A] if (schedule_work(...)) {
> [B] sock_hold(sk);
> return true;
> }
>
> Problem is that mptcp_worker() can run immediately and complete before [B]
>
> We need instead :
>
> sock_hold(sk);
> if (schedule_work(...))
> return true;
> sock_put(sk);
Thank you for having released the syzbot issue with the fix! That's way
easier for us when the fix is provided with the bug report! :-D
The modifications look good to me:
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
This patch can be applied to -net directly, ideally with:
Cc: stable@vger.kernel.org
(Just for me to be able to track issues with the backports. If it cannot
be added, I can also track it "manually" if preferred.)
Cheers,
Matt
--
Sponsored by the NGI0 Core fund.
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