Re: [PATCH net v2 2/2] mptcp: diag: bound listener bucket lock hold

[Eric Dumazet]

On Tue, Sep 1, 2026 at 2:54 PM Zihan Xi <zihanx@xxxxxxxxxx> wrote:
>
> MPTCP listener diag dumping reuses sk_diag_dump(), which executes
> inet_diag_bc_sk() before filling the netlink reply. The listener walk in
> mptcp_diag_dump_listeners() currently performs that work while holding the
> listener bucket lock.
>
> The time spent under the listener bucket lock can therefore grow with the
> number of sockets visited and with per-socket dump work. The resume state
> also requires later batches to revisit the bucket prefix.
>
> Fix this by collecting only referenced listener sockets while holding the
> bucket lock. After dropping it, re-check the listener properties, obtain
> the parent MPTCP socket reference, and call sk_diag_dump(). Keep a
> referenced cursor so later batches resume after the previous listener
> instead of rescanning the bucket head. Validate a cursor against the
> current listener bucket and TCP_LISTEN state before resuming from it.
> After dropping the lock, read icsk_ulp_data with rcu_dereference().
>
> Fixes: 4fa39b701ce9 ("mptcp: listen diag dump support")
> Cc: stable@xxxxxxxxxxxxxxx
> Reported-by: Vega <vega@xxxxxxxxxx>
> Assisted-by: Codex:gpt-5.4
> Signed-off-by: Zihan Xi <zihanx@xxxxxxxxxx>

pw-bot: rejected

Please limit the complexity of filters.

Anyone needing complex filters will implement them in user space.