Commit 57fc0f1c authored by Paolo Abeni's avatar Paolo Abeni Committed by Jakub Kicinski
Browse files

mptcp: ensure listener is unhashed before updating the sk status 



The MPTCP protocol access the listener subflow in a lockless
manner in a couple of places (poll, diag). That works only if
the msk itself leaves the listener status only after that the
subflow itself has been closed/disconnected. Otherwise we risk
deadlock in diag, as reported by Christoph.

Address the issue ensuring that the first subflow (the listener
one) is always disconnected before updating the msk socket status.

Reported-by: default avatarChristoph Paasch <cpaasch@apple.com>
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/407


Fixes: b29fcfb5 ("mptcp: full disconnect implementation")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
Reviewed-by: default avatarMatthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: default avatarMatthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent b7535cfe

net/mptcp/pm_netlink.c

+1 −0
Original line number Diff line number Diff line
@@ -1047,6 +1047,7 @@ static int mptcp_pm_nl_create_listen_socket(struct sock *sk, 
	if (err)

		return err;



	inet_sk_state_store(newsk, TCP_LISTEN);

	err = kernel_listen(ssock, backlog);

	if (err)

		return err;

net/mptcp/protocol.c

+19 −12
Original line number Diff line number Diff line
@@ -2368,13 +2368,6 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk, 
		kfree_rcu(subflow, rcu);

	} else {

		/* otherwise tcp will dispose of the ssk and subflow ctx */

		if (ssk->sk_state == TCP_LISTEN) {

			tcp_set_state(ssk, TCP_CLOSE);

			mptcp_subflow_queue_clean(sk, ssk);

			inet_csk_listen_stop(ssk);

			mptcp_event_pm_listener(ssk, MPTCP_EVENT_LISTENER_CLOSED);

		}



		__tcp_close(ssk, 0);



		/* close acquired an extra ref */
@@ -2902,10 +2895,24 @@ static __poll_t mptcp_check_readable(struct mptcp_sock *msk) 
	return EPOLLIN | EPOLLRDNORM;

}



static void mptcp_listen_inuse_dec(struct sock *sk)

static void mptcp_check_listen_stop(struct sock *sk)

{

	if (inet_sk_state_load(sk) == TCP_LISTEN)

	struct sock *ssk;



	if (inet_sk_state_load(sk) != TCP_LISTEN)

		return;



	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);

	ssk = mptcp_sk(sk)->first;

	if (WARN_ON_ONCE(!ssk || inet_sk_state_load(ssk) != TCP_LISTEN))

		return;



	lock_sock_nested(ssk, SINGLE_DEPTH_NESTING);

	mptcp_subflow_queue_clean(sk, ssk);

	inet_csk_listen_stop(ssk);

	mptcp_event_pm_listener(ssk, MPTCP_EVENT_LISTENER_CLOSED);

	tcp_set_state(ssk, TCP_CLOSE);

	release_sock(ssk);

}



bool __mptcp_close(struct sock *sk, long timeout)
@@ -2918,7 +2925,7 @@ bool __mptcp_close(struct sock *sk, long timeout) 
	WRITE_ONCE(sk->sk_shutdown, SHUTDOWN_MASK);



	if ((1 << sk->sk_state) & (TCPF_LISTEN | TCPF_CLOSE)) {

		mptcp_listen_inuse_dec(sk);

		mptcp_check_listen_stop(sk);

		inet_sk_state_store(sk, TCP_CLOSE);

		goto cleanup;

	}
@@ -3035,7 +3042,7 @@ static int mptcp_disconnect(struct sock *sk, int flags) 
	if (msk->fastopening)

		return -EBUSY;



	mptcp_listen_inuse_dec(sk);

	mptcp_check_listen_stop(sk);

	inet_sk_state_store(sk, TCP_CLOSE);



	mptcp_stop_timer(sk);