1 files changed, 50 insertions, 24 deletions

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 06c5872e3b00..b998e9df53ce 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2315,7 +2315,26 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
 			      unsigned int flags)
 {
 	struct mptcp_sock *msk = mptcp_sk(sk);
-	bool need_push, dispose_it;
+	bool dispose_it, need_push = false;
+
+	/* If the first subflow moved to a close state before accept, e.g. due
+	 * to an incoming reset, mptcp either:
+	 * - if either the subflow or the msk are dead, destroy the context
+	 *   (the subflow socket is deleted by inet_child_forget) and the msk
+	 * - otherwise do nothing at the moment and take action at accept and/or
+	 *   listener shutdown - user-space must be able to accept() the closed
+	 *   socket.
+	 */
+	if (msk->in_accept_queue && msk->first == ssk) {
+		if (!sock_flag(sk, SOCK_DEAD) && !sock_flag(ssk, SOCK_DEAD))
+			return;
+
+		/* ensure later check in mptcp_worker() will dispose the msk */
+		sock_set_flag(sk, SOCK_DEAD);
+		lock_sock_nested(ssk, SINGLE_DEPTH_NESTING);
+		mptcp_subflow_drop_ctx(ssk);
+		goto out_release;
+	}
 
 	dispose_it = !msk->subflow || ssk != msk->subflow->sk;
 	if (dispose_it)
@@ -2351,28 +2370,22 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
 	if (!inet_csk(ssk)->icsk_ulp_ops) {
 		WARN_ON_ONCE(!sock_flag(ssk, SOCK_DEAD));
 		kfree_rcu(subflow, rcu);
-	} else if (msk->in_accept_queue && msk->first == ssk) {
-		/* if the first subflow moved to a close state, e.g. due to
-		 * incoming reset and we reach here before inet_child_forget()
-		 * the TCP stack could later try to close it via
-		 * inet_csk_listen_stop(), or deliver it to the user space via
-		 * accept().
-		 * We can't delete the subflow - or risk a double free - nor let
-		 * the msk survive - or will be leaked in the non accept scenario:
-		 * fallback and let TCP cope with the subflow cleanup.
-		 */
-		WARN_ON_ONCE(sock_flag(ssk, SOCK_DEAD));
-		mptcp_subflow_drop_ctx(ssk);
 	} else {
 		/* otherwise tcp will dispose of the ssk and subflow ctx */
-		if (ssk->sk_state == TCP_LISTEN)
+		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 */
 		__sock_put(ssk);
 	}
+
+out_release:
 	release_sock(ssk);
 
 	sock_put(ssk);
@@ -2427,21 +2440,14 @@ static void __mptcp_close_subflow(struct sock *sk)
 		mptcp_close_ssk(sk, ssk, subflow);
 	}
 
-	/* if the MPC subflow has been closed before the msk is accepted,
-	 * msk will never be accept-ed, close it now
-	 */
-	if (!msk->first && msk->in_accept_queue) {
-		sock_set_flag(sk, SOCK_DEAD);
-		inet_sk_state_store(sk, TCP_CLOSE);
-	}
 }
 
-static bool mptcp_check_close_timeout(const struct sock *sk)
+static bool mptcp_should_close(const struct sock *sk)
 {
 	s32 delta = tcp_jiffies32 - inet_csk(sk)->icsk_mtup.probe_timestamp;
 	struct mptcp_subflow_context *subflow;
 
-	if (delta >= TCP_TIMEWAIT_LEN)
+	if (delta >= TCP_TIMEWAIT_LEN || mptcp_sk(sk)->in_accept_queue)
 		return true;
 
 	/* if all subflows are in closed status don't bother with additional
@@ -2649,7 +2655,7 @@ static void mptcp_worker(struct work_struct *work)
 	 * even if it is orphaned and in FIN_WAIT2 state
 	 */
 	if (sock_flag(sk, SOCK_DEAD)) {
-		if (mptcp_check_close_timeout(sk)) {
+		if (mptcp_should_close(sk)) {
 			inet_sk_state_store(sk, TCP_CLOSE);
 			mptcp_do_fastclose(sk);
 		}
@@ -2895,6 +2901,14 @@ static void __mptcp_destroy_sock(struct sock *sk)
 	sock_put(sk);
 }
 
+void __mptcp_unaccepted_force_close(struct sock *sk)
+{
+	sock_set_flag(sk, SOCK_DEAD);
+	inet_sk_state_store(sk, TCP_CLOSE);
+	mptcp_do_fastclose(sk);
+	__mptcp_destroy_sock(sk);
+}
+
 static __poll_t mptcp_check_readable(struct mptcp_sock *msk)
 {
 	/* Concurrent splices from sk_receive_queue into receive_queue will
@@ -3733,6 +3747,18 @@ static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
 			if (!ssk->sk_socket)
 				mptcp_sock_graft(ssk, newsock);
 		}
+
+		/* Do late cleanup for the first subflow as necessary. Also
+		 * deal with bad peers not doing a complete shutdown.
+		 */
+		if (msk->first &&
+		    unlikely(inet_sk_state_load(msk->first) == TCP_CLOSE)) {
+			__mptcp_close_ssk(newsk, msk->first,
+					  mptcp_subflow_ctx(msk->first), 0);
+			if (unlikely(list_empty(&msk->conn_list)))
+				inet_sk_state_store(newsk, TCP_CLOSE);
+		}
+
 		release_sock(newsk);
 	}