Re: [PATCH net] mptcp: pm: in-kernel: fix C-flag endpoint accounting on family mismatch

[Matthieu Baerts <matttbe@kernel.org>]

Hi Yiming Qian,

On 06/10/2026 13:59, Matthieu Baerts wrote:
> Hi Yiming Qian,
> 
> On 06/10/2026 13:42, Yiming Qian wrote:
>> fill_local_addresses_vec_c_flag() clears the endpoint ID bit in
>> id_avail_bitmap before checking whether the endpoint's address family
>> matches the remote ADD_ADDR.  If it does not match, the loop skips the
>> endpoint without incrementing local_addr_used, leaving id_avail_bitmap
>> and local_addr_used inconsistent.
>>
>> Removing that SUBFLOW endpoint later calls
>> __mark_subflow_endp_available(), which sees the cleared bit, expects
>> local_addr_used to be non-zero, and triggers a WARN and, with
>> panic_on_warn=1, a panic.
>>
>> Keep the endpoints that are skipped during this specific C-flag
>> iteration available by tracking them in a local bitmap passed to
>> select_local_address(), instead of clearing their IDs in the per-socket
>> bitmap.  Only IDs of endpoints actually used for a subflow are now
>> cleared and accounted for.
> 
> Thank you for the patch.

Just to avoid a deadlock, do you plan to send a v2, or do you prefer if
someone else does that?

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