Merge branch 'tipc-topology-fixes'

Parthasarathy Bhuvaragan says:

====================
tipc: topology server fixes for nametable soft lockup

In this series, we revert the commit 333f796235a527 ("tipc: fix a
race condition leading to subscriber refcnt bug") and provide an
alternate solution to fix the race conditions in commits 2-4.

We have to do this as the above commit introduced a nametbl soft
lockup at module exit as described by patch#4.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 99 insertions, 83 deletions

diff --git a/net/tipc/node.c b/net/tipc/node.c
index 9d2f4c2b08ab..27753325e06e 100644
--- a/net/tipc/node.c
+++ b/net/tipc/node.c
@@ -263,6 +263,11 @@ static void tipc_node_write_lock(struct tipc_node *n)
 	write_lock_bh(&n->lock);
 }
 
+static void tipc_node_write_unlock_fast(struct tipc_node *n)
+{
+	write_unlock_bh(&n->lock);
+}
+
 static void tipc_node_write_unlock(struct tipc_node *n)
 {
 	struct net *net = n->net;
@@ -417,7 +422,7 @@ void tipc_node_subscribe(struct net *net, struct list_head *subscr, u32 addr)
 	}
 	tipc_node_write_lock(n);
 	list_add_tail(subscr, &n->publ_list);
-	tipc_node_write_unlock(n);
+	tipc_node_write_unlock_fast(n);
 	tipc_node_put(n);
 }
 
@@ -435,7 +440,7 @@ void tipc_node_unsubscribe(struct net *net, struct list_head *subscr, u32 addr)
 	}
 	tipc_node_write_lock(n);
 	list_del_init(subscr);
-	tipc_node_write_unlock(n);
+	tipc_node_write_unlock_fast(n);
 	tipc_node_put(n);
 }
 
diff --git a/net/tipc/server.c b/net/tipc/server.c
index 215849ce453d..3cd6402e812c 100644
--- a/net/tipc/server.c
+++ b/net/tipc/server.c
@@ -86,12 +86,12 @@ struct outqueue_entry {
 static void tipc_recv_work(struct work_struct *work);
 static void tipc_send_work(struct work_struct *work);
 static void tipc_clean_outqueues(struct tipc_conn *con);
-static void tipc_sock_release(struct tipc_conn *con);
 
 static void tipc_conn_kref_release(struct kref *kref)
 {
 	struct tipc_conn *con = container_of(kref, struct tipc_conn, kref);
-	struct sockaddr_tipc *saddr = con->server->saddr;
+	struct tipc_server *s = con->server;
+	struct sockaddr_tipc *saddr = s->saddr;
 	struct socket *sock = con->sock;
 	struct sock *sk;
 
@@ -103,9 +103,13 @@ static void tipc_conn_kref_release(struct kref *kref)
 		}
 		saddr->scope = -TIPC_NODE_SCOPE;
 		kernel_bind(sock, (struct sockaddr *)saddr, sizeof(*saddr));
-		tipc_sock_release(con);
 		sock_release(sock);
 		con->sock = NULL;
+
+		spin_lock_bh(&s->idr_lock);
+		idr_remove(&s->conn_idr, con->conid);
+		s->idr_in_use--;
+		spin_unlock_bh(&s->idr_lock);
 	}
 
 	tipc_clean_outqueues(con);
@@ -128,8 +132,10 @@ static struct tipc_conn *tipc_conn_lookup(struct tipc_server *s, int conid)
 
 	spin_lock_bh(&s->idr_lock);
 	con = idr_find(&s->conn_idr, conid);
-	if (con)
+	if (con && test_bit(CF_CONNECTED, &con->flags))
 		conn_get(con);
+	else
+		con = NULL;
 	spin_unlock_bh(&s->idr_lock);
 	return con;
 }
@@ -186,26 +192,15 @@ static void tipc_unregister_callbacks(struct tipc_conn *con)
 	write_unlock_bh(&sk->sk_callback_lock);
 }
 
-static void tipc_sock_release(struct tipc_conn *con)
-{
-	struct tipc_server *s = con->server;
-
-	if (con->conid)
-		s->tipc_conn_release(con->conid, con->usr_data);
-
-	tipc_unregister_callbacks(con);
-}
-
 static void tipc_close_conn(struct tipc_conn *con)
 {
 	struct tipc_server *s = con->server;
 
 	if (test_and_clear_bit(CF_CONNECTED, &con->flags)) {
+		tipc_unregister_callbacks(con);
 
-		spin_lock_bh(&s->idr_lock);
-		idr_remove(&s->conn_idr, con->conid);
-		s->idr_in_use--;
-		spin_unlock_bh(&s->idr_lock);
+		if (con->conid)
+			s->tipc_conn_release(con->conid, con->usr_data);
 
 		/* We shouldn't flush pending works as we may be in the
 		 * thread. In fact the races with pending rx/tx work structs
@@ -458,6 +453,11 @@ int tipc_conn_sendmsg(struct tipc_server *s, int conid,
 	if (!con)
 		return -EINVAL;
 
+	if (!test_bit(CF_CONNECTED, &con->flags)) {
+		conn_put(con);
+		return 0;
+	}
+
 	e = tipc_alloc_entry(data, len);
 	if (!e) {
 		conn_put(con);
@@ -471,12 +471,8 @@ int tipc_conn_sendmsg(struct tipc_server *s, int conid,
 	list_add_tail(&e->list, &con->outqueue);
 	spin_unlock_bh(&con->outqueue_lock);
 
-	if (test_bit(CF_CONNECTED, &con->flags)) {
-		if (!queue_work(s->send_wq, &con->swork))
-			conn_put(con);
-	} else {
+	if (!queue_work(s->send_wq, &con->swork))
 		conn_put(con);
-	}
 	return 0;
 }
 
@@ -500,7 +496,7 @@ static void tipc_send_to_sock(struct tipc_conn *con)
 	int ret;
 
 	spin_lock_bh(&con->outqueue_lock);
-	while (1) {
+	while (test_bit(CF_CONNECTED, &con->flags)) {
 		e = list_entry(con->outqueue.next, struct outqueue_entry,
 			       list);
 		if ((struct list_head *) e == &con->outqueue)
@@ -623,14 +619,12 @@ int tipc_server_start(struct tipc_server *s)
 void tipc_server_stop(struct tipc_server *s)
 {
 	struct tipc_conn *con;
-	int total = 0;
 	int id;
 
 	spin_lock_bh(&s->idr_lock);
-	for (id = 0; total < s->idr_in_use; id++) {
+	for (id = 0; s->idr_in_use; id++) {
 		con = idr_find(&s->conn_idr, id);
 		if (con) {
-			total++;
 			spin_unlock_bh(&s->idr_lock);
 			tipc_close_conn(con);
 			spin_lock_bh(&s->idr_lock);
diff --git a/net/tipc/subscr.c b/net/tipc/subscr.c
index 0dd02244e21d..9d94e65d0894 100644
--- a/net/tipc/subscr.c
+++ b/net/tipc/subscr.c
@@ -54,6 +54,8 @@ struct tipc_subscriber {
 
 static void tipc_subscrp_delete(struct tipc_subscription *sub);
 static void tipc_subscrb_put(struct tipc_subscriber *subscriber);
+static void tipc_subscrp_put(struct tipc_subscription *subscription);
+static void tipc_subscrp_get(struct tipc_subscription *subscription);
 
 /**
  * htohl - convert value to endianness used by destination
@@ -123,6 +125,7 @@ void tipc_subscrp_report_overlap(struct tipc_subscription *sub, u32 found_lower,
 {
 	struct tipc_name_seq seq;
 
+	tipc_subscrp_get(sub);
 	tipc_subscrp_convert_seq(&sub->evt.s.seq, sub->swap, &seq);
 	if (!tipc_subscrp_check_overlap(&seq, found_lower, found_upper))
 		return;
@@ -132,30 +135,23 @@ void tipc_subscrp_report_overlap(struct tipc_subscription *sub, u32 found_lower,
 
 	tipc_subscrp_send_event(sub, found_lower, found_upper, event, port_ref,
 				node);
+	tipc_subscrp_put(sub);
 }
 
 static void tipc_subscrp_timeout(unsigned long data)
 {
 	struct tipc_subscription *sub = (struct tipc_subscription *)data;
-	struct tipc_subscriber *subscriber = sub->subscriber;
 
 	/* Notify subscriber of timeout */
 	tipc_subscrp_send_event(sub, sub->evt.s.seq.lower, sub->evt.s.seq.upper,
 				TIPC_SUBSCR_TIMEOUT, 0, 0);
 
-	spin_lock_bh(&subscriber->lock);
-	tipc_subscrp_delete(sub);
-	spin_unlock_bh(&subscriber->lock);
-
-	tipc_subscrb_put(subscriber);
+	tipc_subscrp_put(sub);
 }
 
 static void tipc_subscrb_kref_release(struct kref *kref)
 {
-	struct tipc_subscriber *subcriber = container_of(kref,
-					    struct tipc_subscriber, kref);
-
-	kfree(subcriber);
+	kfree(container_of(kref,struct tipc_subscriber, kref));
 }
 
 static void tipc_subscrb_put(struct tipc_subscriber *subscriber)
@@ -168,6 +164,59 @@ static void tipc_subscrb_get(struct tipc_subscriber *subscriber)
 	kref_get(&subscriber->kref);
 }
 
+static void tipc_subscrp_kref_release(struct kref *kref)
+{
+	struct tipc_subscription *sub = container_of(kref,
+						     struct tipc_subscription,
+						     kref);
+	struct tipc_net *tn = net_generic(sub->net, tipc_net_id);
+	struct tipc_subscriber *subscriber = sub->subscriber;
+
+	spin_lock_bh(&subscriber->lock);
+	tipc_nametbl_unsubscribe(sub);
+	list_del(&sub->subscrp_list);
+	atomic_dec(&tn->subscription_count);
+	spin_unlock_bh(&subscriber->lock);
+	kfree(sub);
+	tipc_subscrb_put(subscriber);
+}
+
+static void tipc_subscrp_put(struct tipc_subscription *subscription)
+{
+	kref_put(&subscription->kref, tipc_subscrp_kref_release);
+}
+
+static void tipc_subscrp_get(struct tipc_subscription *subscription)
+{
+	kref_get(&subscription->kref);
+}
+
+/* tipc_subscrb_subscrp_delete - delete a specific subscription or all
+ * subscriptions for a given subscriber.
+ */
+static void tipc_subscrb_subscrp_delete(struct tipc_subscriber *subscriber,
+					struct tipc_subscr *s)
+{
+	struct list_head *subscription_list = &subscriber->subscrp_list;
+	struct tipc_subscription *sub, *temp;
+
+	spin_lock_bh(&subscriber->lock);
+	list_for_each_entry_safe(sub, temp, subscription_list,  subscrp_list) {
+		if (s && memcmp(s, &sub->evt.s, sizeof(struct tipc_subscr)))
+			continue;
+
+		tipc_subscrp_get(sub);
+		spin_unlock_bh(&subscriber->lock);
+		tipc_subscrp_delete(sub);
+		tipc_subscrp_put(sub);
+		spin_lock_bh(&subscriber->lock);
+
+		if (s)
+			break;
+	}
+	spin_unlock_bh(&subscriber->lock);
+}
+
 static struct tipc_subscriber *tipc_subscrb_create(int conid)
 {
 	struct tipc_subscriber *subscriber;
@@ -177,8 +226,8 @@ static struct tipc_subscriber *tipc_subscrb_create(int conid)
 		pr_warn("Subscriber rejected, no memory\n");
 		return NULL;
 	}
-	kref_init(&subscriber->kref);
 	INIT_LIST_HEAD(&subscriber->subscrp_list);
+	kref_init(&subscriber->kref);
 	subscriber->conid = conid;
 	spin_lock_init(&subscriber->lock);
 
@@ -187,55 +236,22 @@ static struct tipc_subscriber *tipc_subscrb_create(int conid)
 
 static void tipc_subscrb_delete(struct tipc_subscriber *subscriber)
 {
-	struct tipc_subscription *sub, *temp;
-	u32 timeout;
-
-	spin_lock_bh(&subscriber->lock);
-	/* Destroy any existing subscriptions for subscriber */
-	list_for_each_entry_safe(sub, temp, &subscriber->subscrp_list,
-				 subscrp_list) {
-		timeout = htohl(sub->evt.s.timeout, sub->swap);
-		if ((timeout == TIPC_WAIT_FOREVER) || del_timer(&sub->timer)) {
-			tipc_subscrp_delete(sub);
-			tipc_subscrb_put(subscriber);
-		}
-	}
-	spin_unlock_bh(&subscriber->lock);
-
+	tipc_subscrb_subscrp_delete(subscriber, NULL);
 	tipc_subscrb_put(subscriber);
 }
 
 static void tipc_subscrp_delete(struct tipc_subscription *sub)
 {
-	struct tipc_net *tn = net_generic(sub->net, tipc_net_id);
+	u32 timeout = htohl(sub->evt.s.timeout, sub->swap);
 
-	tipc_nametbl_unsubscribe(sub);
-	list_del(&sub->subscrp_list);
-	kfree(sub);
-	atomic_dec(&tn->subscription_count);
+	if (timeout == TIPC_WAIT_FOREVER || del_timer(&sub->timer))
+		tipc_subscrp_put(sub);
 }
 
 static void tipc_subscrp_cancel(struct tipc_subscr *s,
 				struct tipc_subscriber *subscriber)
 {
-	struct tipc_subscription *sub, *temp;
-	u32 timeout;
-
-	spin_lock_bh(&subscriber->lock);
-	/* Find first matching subscription, exit if not found */
-	list_for_each_entry_safe(sub, temp, &subscriber->subscrp_list,
-				 subscrp_list) {
-		if (!memcmp(s, &sub->evt.s, sizeof(struct tipc_subscr))) {
-			timeout = htohl(sub->evt.s.timeout, sub->swap);
-			if ((timeout == TIPC_WAIT_FOREVER) ||
-			    del_timer(&sub->timer)) {
-				tipc_subscrp_delete(sub);
-				tipc_subscrb_put(subscriber);
-			}
-			break;
-		}
-	}
-	spin_unlock_bh(&subscriber->lock);
+	tipc_subscrb_subscrp_delete(subscriber, s);
 }
 
 static struct tipc_subscription *tipc_subscrp_create(struct net *net,
@@ -272,6 +288,7 @@ static struct tipc_subscription *tipc_subscrp_create(struct net *net,
 	sub->swap = swap;
 	memcpy(&sub->evt.s, s, sizeof(*s));
 	atomic_inc(&tn->subscription_count);
+	kref_init(&sub->kref);
 	return sub;
 }
 
@@ -288,17 +305,16 @@ static void tipc_subscrp_subscribe(struct net *net, struct tipc_subscr *s,
 
 	spin_lock_bh(&subscriber->lock);
 	list_add(&sub->subscrp_list, &subscriber->subscrp_list);
-	tipc_subscrb_get(subscriber);
 	sub->subscriber = subscriber;
 	tipc_nametbl_subscribe(sub);
+	tipc_subscrb_get(subscriber);
 	spin_unlock_bh(&subscriber->lock);
 
+	setup_timer(&sub->timer, tipc_subscrp_timeout, (unsigned long)sub);
 	timeout = htohl(sub->evt.s.timeout, swap);
-	if (timeout == TIPC_WAIT_FOREVER)
-		return;
 
-	setup_timer(&sub->timer, tipc_subscrp_timeout, (unsigned long)sub);
-	mod_timer(&sub->timer, jiffies + msecs_to_jiffies(timeout));
+	if (timeout != TIPC_WAIT_FOREVER)
+		mod_timer(&sub->timer, jiffies + msecs_to_jiffies(timeout));
 }
 
 /* Handle one termination request for the subscriber */
diff --git a/net/tipc/subscr.h b/net/tipc/subscr.h
index be60103082c9..ffdc214c117a 100644
--- a/net/tipc/subscr.h
+++ b/net/tipc/subscr.h
@@ -57,6 +57,7 @@ struct tipc_subscriber;
  * @evt: template for events generated by subscription
  */
 struct tipc_subscription {
+	struct kref kref;
 	struct tipc_subscriber *subscriber;
 	struct net *net;
 	struct timer_list timer;