Commit c2b2ae39 authored by Paolo Abeni's avatar Paolo Abeni Committed by Jakub Kicinski
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mptcp: handle correctly disconnect() failures 



Currently the mptcp code has assumes that disconnect() can fail only
at mptcp_sendmsg_fastopen() time - to avoid a deadlock scenario - and
don't even bother returning an error code.

Soon mptcp_disconnect() will handle more error conditions: let's track
them explicitly.

As a bonus, explicitly annotate TCP-level disconnect as not failing:
the mptcp code never blocks for event on the subflows.

Fixes: 7d803344 ("mptcp: fix deadlock in fastopen error path")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
Tested-by: default avatarChristoph Paasch <cpaasch@apple.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 59bb14bd

net/mptcp/protocol.c

+14 −6
Original line number Diff line number Diff line
@@ -1727,7 +1727,13 @@ static int mptcp_sendmsg_fastopen(struct sock *sk, struct msghdr *msg, 
		if (ret && ret != -EINPROGRESS && ret != -ERESTARTSYS && ret != -EINTR)

			*copied_syn = 0;

	} else if (ret && ret != -EINPROGRESS) {

		mptcp_disconnect(sk, 0);

		/* The disconnect() op called by tcp_sendmsg_fastopen()/

		 * __inet_stream_connect() can fail, due to looking check,

		 * see mptcp_disconnect().

		 * Attempt it again outside the problematic scope.

		 */

		if (!mptcp_disconnect(sk, 0))

			sk->sk_socket->state = SS_UNCONNECTED;

	}

	inet_sk(sk)->defer_connect = 0;
@@ -2389,7 +2395,10 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk, 


	need_push = (flags & MPTCP_CF_PUSH) && __mptcp_retransmit_pending_data(sk);

	if (!dispose_it) {

		tcp_disconnect(ssk, 0);

		/* The MPTCP code never wait on the subflow sockets, TCP-level

		 * disconnect should never fail

		 */

		WARN_ON_ONCE(tcp_disconnect(ssk, 0));

		msk->subflow->state = SS_UNCONNECTED;

		mptcp_subflow_ctx_reset(subflow);

		release_sock(ssk);
@@ -2812,7 +2821,7 @@ void mptcp_subflow_shutdown(struct sock *sk, struct sock *ssk, int how) 
			break;

		fallthrough;

	case TCP_SYN_SENT:

		tcp_disconnect(ssk, O_NONBLOCK);

		WARN_ON_ONCE(tcp_disconnect(ssk, O_NONBLOCK));

		break;

	default:

		if (__mptcp_check_fallback(mptcp_sk(sk))) {
@@ -3075,11 +3084,10 @@ static int mptcp_disconnect(struct sock *sk, int flags) 


	/* We are on the fastopen error path. We can't call straight into the

	 * subflows cleanup code due to lock nesting (we are already under

	 * msk->firstsocket lock). Do nothing and leave the cleanup to the

	 * caller.

	 * msk->firstsocket lock).

	 */

	if (msk->fastopening)

		return 0;

		return -EBUSY;



	mptcp_listen_inuse_dec(sk);

	inet_sk_state_store(sk, TCP_CLOSE);