Merge branch 'mptcp-fixes'

Paolo Abeni says:

====================
mptcp: a bunch of fixes

This series includes a few fixes following-up the
recent code refactor for the MPTCP RX and TX paths.

Boundling them together, since the fixes are somewhat
related.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

net/mptcp/options.c

@@ -802,7 +802,12 @@ static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
 	mptcp_subflow_fully_established(subflow, mp_opt);
 
 fully_established:
-	if (likely(subflow->pm_notified))
+	/* if the subflow is not already linked into the conn_list, we can't
+	 * notify the PM: this subflow is still on the listener queue
+	 * and the PM possibly acquiring the subflow lock could race with
+	 * the listener close
+	 */
+	if (likely(subflow->pm_notified) || list_empty(&subflow->node))
 		return true;
 
 	subflow->pm_notified = 1;

net/mptcp/pm.c

@@ -126,8 +126,14 @@ void mptcp_pm_fully_established(struct mptcp_sock *msk)
 
 	spin_lock_bh(&pm->lock);
 
-	if (READ_ONCE(pm->work_pending))
+	/* mptcp_pm_fully_established() can be invoked by multiple
+	 * racing paths - accept() and check_fully_established()
+	 * be sure to serve this event only once.
+	 */
+	if (READ_ONCE(pm->work_pending) &&
+	    !(msk->pm.status & BIT(MPTCP_PM_ALREADY_ESTABLISHED)))
 		mptcp_pm_schedule_work(msk, MPTCP_PM_ESTABLISHED);
+	msk->pm.status |= BIT(MPTCP_PM_ALREADY_ESTABLISHED);
 
 	spin_unlock_bh(&pm->lock);
 }

net/mptcp/protocol.c

@@ -701,6 +701,13 @@ void mptcp_data_ready(struct sock *sk, struct sock *ssk)
 	int sk_rbuf, ssk_rbuf;
 	bool wake;
 
+	/* The peer can send data while we are shutting down this
+	 * subflow at msk destruction time, but we must avoid enqueuing
+	 * more data to the msk receive queue
+	 */
+	if (unlikely(subflow->disposable))
+		return;
+
 	/* move_skbs_to_msk below can legitly clear the data_avail flag,
 	 * but we will need later to properly woke the reader, cache its
 	 * value
@@ -2119,6 +2126,8 @@ void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
 		sock_orphan(ssk);
 	}
 
+	subflow->disposable = 1;
+
 	/* if ssk hit tcp_done(), tcp_cleanup_ulp() cleared the related ops
 	 * the ssk has been already destroyed, we just need to release the
 	 * reference owned by msk;
@@ -2126,8 +2135,7 @@ void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
 	if (!inet_csk(ssk)->icsk_ulp_ops) {
 		kfree_rcu(subflow, rcu);
 	} else {
-		/* otherwise ask tcp do dispose of ssk and subflow ctx */
-		subflow->disposable = 1;
+		/* otherwise tcp will dispose of the ssk and subflow ctx */
 		__tcp_close(ssk, 0);
 
 		/* close acquired an extra ref */
@@ -3208,6 +3216,17 @@ static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
 		bool slowpath;
 
 		slowpath = lock_sock_fast(newsk);
+
+		/* PM/worker can now acquire the first subflow socket
+		 * lock without racing with listener queue cleanup,
+		 * we can notify it, if needed.
+		 */
+		subflow = mptcp_subflow_ctx(msk->first);
+		list_add(&subflow->node, &msk->conn_list);
+		sock_hold(msk->first);
+		if (mptcp_is_fully_established(newsk))
+			mptcp_pm_fully_established(msk);
+
 		mptcp_copy_inaddrs(newsk, msk->first);
 		mptcp_rcv_space_init(msk, msk->first);
 

net/mptcp/protocol.h

@@ -165,6 +165,7 @@ enum mptcp_pm_status {
 	MPTCP_PM_ADD_ADDR_SEND_ACK,
 	MPTCP_PM_RM_ADDR_RECEIVED,
 	MPTCP_PM_ESTABLISHED,
+	MPTCP_PM_ALREADY_ESTABLISHED,	/* persistent status, set after ESTABLISHED event */
 	MPTCP_PM_SUBFLOW_ESTABLISHED,
 };
 

net/mptcp/subflow.c

@@ -614,8 +614,9 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 			 */
 			inet_sk_state_store((void *)new_msk, TCP_ESTABLISHED);
 
-			/* link the newly created socket to the msk */
-			mptcp_add_pending_subflow(mptcp_sk(new_msk), ctx);
+			/* record the newly created socket as the first msk
+			 * subflow, but don't link it yet into conn_list
+			 */
 			WRITE_ONCE(mptcp_sk(new_msk)->first, child);
 
 			/* new mpc subflow takes ownership of the newly
@@ -1148,13 +1149,18 @@ int __mptcp_subflow_connect(struct sock *sk, const struct mptcp_addr_info *loc,
 	subflow->request_bkup = !!(loc->flags & MPTCP_PM_ADDR_FLAG_BACKUP);
 	mptcp_info2sockaddr(remote, &addr);
 
+	mptcp_add_pending_subflow(msk, subflow);
 	err = kernel_connect(sf, (struct sockaddr *)&addr, addrlen, O_NONBLOCK);
 	if (err && err != -EINPROGRESS)
-		goto failed;
+		goto failed_unlink;
 
-	mptcp_add_pending_subflow(msk, subflow);
 	return err;
 
+failed_unlink:
+	spin_lock_bh(&msk->join_list_lock);
+	list_del(&subflow->node);
+	spin_unlock_bh(&msk->join_list_lock);
+
 failed:
 	subflow->disposable = 1;
 	sock_release(sf);
@@ -1333,9 +1339,10 @@ static void subflow_ulp_release(struct sock *ssk)
 	sk = ctx->conn;
 	if (sk) {
 		/* if the msk has been orphaned, keep the ctx
-		 * alive, will be freed by mptcp_done()
+		 * alive, will be freed by __mptcp_close_ssk(),
+		 * when the subflow is still unaccepted
 		 */
-		release = ctx->disposable;
+		release = ctx->disposable || list_empty(&ctx->node);
 		sock_put(sk);
 	}