From: Paolo Abeni <pabeni@xxxxxxxxxx> commit 52557dbc7538ecceb27ef2206719a47a8039a335 upstream. MPJ subflows are not exposed as fds to user spaces. As such, incoming MPJ subflows are removed from the accept queue by tcp_check_req()/tcp_get_cookie_sock(). Later tcp_child_process() invokes subflow_data_ready() on the parent socket regardless of the subflow kind, leading to poll wakeups even if the later accept will block. Address the issue by double-checking the queue state before waking the user-space. Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/164 Reported-by: Dr. David Alan Gilbert <dgilbert@xxxxxxxxxx> Fixes: f296234c98a8 ("mptcp: Add handling of incoming MP_JOIN requests") Reviewed-by: Mat Martineau <mathew.j.martineau@xxxxxxxxxxxxxxx> Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx> Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/mptcp/subflow.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -981,6 +981,12 @@ static void subflow_data_ready(struct so msk = mptcp_sk(parent); if (state & TCPF_LISTEN) { + /* MPJ subflow are removed from accept queue before reaching here, + * avoid stray wakeups + */ + if (reqsk_queue_empty(&inet_csk(sk)->icsk_accept_queue)) + return; + set_bit(MPTCP_DATA_READY, &msk->flags); parent->sk_data_ready(parent); return;
