Re: [PATCH mptcp-net] mptcp: bpf: fix type confusion in bpf_mptcp_sock_from_subflow()

[Matthieu Baerts <matttbe@kernel.org>]

Hi Kuniyuki,

On 30/04/2026 22:35, Kuniyuki Iwashima wrote:
> On Thu, Apr 30, 2026 at 1:27 PM Matthieu Baerts (NGI0)
> <matttbe@kernel.org> wrote:
>>
>> bpf_mptcp_sock_from_subflow() only checks if sk->sk_protocol is
>> IPPROTO_TCP, but RAW socket can bypass it:
>>
>>   socket(AF_INET, SOCK_RAW, IPPROTO_TCP)
>>
>> In this case, it would NOT be valid to call sk_is_mptcp() which will
>> assume sk is a pointer to a struct tcp_sock, and wrongly checks for:
>> tcp_sk(sk)->is_mptcp.
>>
>> This is similar to the modification done on TCP side [1], by Kuniyuki.
>>
>> Fixes: 3bc253c2e652 ("bpf: Add bpf_skc_to_mptcp_sock_proto")
>> Link: https://lore.kernel.org/20260430184405.1227386-1-kuniyu@google.com [1]
>> Cc: Kuniyuki Iwashima <kuniyu@google.com>
>> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
> 
> Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>

Thank you for the review!

If you need to send a v2 of your series to the BPF ML, feel free to
include this patch (without the last sentence, the Link and the Cc
tags). But I can also send it separately later if preferred, up to you.

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