tipc: clean up removal of binding table items

In commit be47e41d77fb ("tipc: fix use-after-free in tipc_nametbl_stop")
we fixed a problem caused by premature release of service range items.

That fix is correct, and solved the problem. However, it doesn't address
the root of the problem, which is that we don't lookup the tipc_service
 -> service_range -> publication items in the correct hierarchical
order.

In this commit we try to make this right, and as a side effect obtain
some code simplification.

Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/name_table.c

@@ -136,12 +136,12 @@ static struct tipc_service *tipc_service_create(u32 type, struct hlist_head *hd)
 }
 
 /**
- * tipc_service_find_range - find service range matching a service instance
+ * tipc_service_first_range - find first service range in tree matching instance
  *
  * Very time-critical, so binary search through range rb tree
  */
-static struct service_range *tipc_service_find_range(struct tipc_service *sc,
-						     u32 instance)
+static struct service_range *tipc_service_first_range(struct tipc_service *sc,
+						      u32 instance)
 {
 	struct rb_node *n = sc->ranges.rb_node;
 	struct service_range *sr;
@@ -158,6 +158,30 @@ static struct service_range *tipc_service_find_range(struct tipc_service *sc,
 	return NULL;
 }
 
+/*  tipc_service_find_range - find service range matching publication parameters
+ */
+static struct service_range *tipc_service_find_range(struct tipc_service *sc,
+						     u32 lower, u32 upper)
+{
+	struct rb_node *n = sc->ranges.rb_node;
+	struct service_range *sr;
+
+	sr = tipc_service_first_range(sc, lower);
+	if (!sr)
+		return NULL;
+
+	/* Look for exact match */
+	for (n = &sr->tree_node; n; n = rb_next(n)) {
+		sr = container_of(n, struct service_range, tree_node);
+		if (sr->upper == upper)
+			break;
+	}
+	if (!n || sr->lower != lower || sr->upper != upper)
+		return NULL;
+
+	return sr;
+}
+
 static struct service_range *tipc_service_create_range(struct tipc_service *sc,
 						       u32 lower, u32 upper)
 {
@@ -238,54 +262,19 @@ err:
 /**
  * tipc_service_remove_publ - remove a publication from a service
  */
-static struct publication *tipc_service_remove_publ(struct net *net,
-						    struct tipc_service *sc,
-						    u32 lower, u32 upper,
-						    u32 node, u32 key,
-						    struct service_range **rng)
+static struct publication *tipc_service_remove_publ(struct service_range *sr,
+						    u32 node, u32 key)
 {
-	struct tipc_subscription *sub, *tmp;
-	struct service_range *sr;
 	struct publication *p;
-	bool found = false;
-	bool last = false;
-	struct rb_node *n;
-
-	sr = tipc_service_find_range(sc, lower);
-	if (!sr)
-		return NULL;
 
-	/* Find exact matching service range */
-	for (n = &sr->tree_node; n; n = rb_next(n)) {
-		sr = container_of(n, struct service_range, tree_node);
-		if (sr->upper == upper)
-			break;
-	}
-	if (!n || sr->lower != lower || sr->upper != upper)
-		return NULL;
-
-	/* Find publication, if it exists */
 	list_for_each_entry(p, &sr->all_publ, all_publ) {
 		if (p->key != key || (node && node != p->node))
 			continue;
-		found = true;
-		break;
+		list_del(&p->all_publ);
+		list_del(&p->local_publ);
+		return p;
 	}
-	if (!found)
-		return NULL;
-
-	list_del(&p->all_publ);
-	list_del(&p->local_publ);
-	if (list_empty(&sr->all_publ))
-		last = true;
-
-	/* Notify any waiting subscriptions */
-	list_for_each_entry_safe(sub, tmp, &sc->subscriptions, service_list) {
-		tipc_sub_report_overlap(sub, p->lower, p->upper, TIPC_WITHDRAWN,
-					p->port, p->node, p->scope, last);
-	}
-	*rng = sr;
-	return p;
+	return NULL;
 }
 
 /**
@@ -376,17 +365,31 @@ struct publication *tipc_nametbl_remove_publ(struct net *net, u32 type,
 					     u32 node, u32 key)
 {
 	struct tipc_service *sc = tipc_service_find(net, type);
+	struct tipc_subscription *sub, *tmp;
 	struct service_range *sr = NULL;
 	struct publication *p = NULL;
+	bool last;
 
 	if (!sc)
 		return NULL;
 
 	spin_lock_bh(&sc->lock);
-	p = tipc_service_remove_publ(net, sc, lower, upper, node, key, &sr);
+	sr = tipc_service_find_range(sc, lower, upper);
+	if (!sr)
+		goto exit;
+	p = tipc_service_remove_publ(sr, node, key);
+	if (!p)
+		goto exit;
+
+	/* Notify any waiting subscriptions */
+	last = list_empty(&sr->all_publ);
+	list_for_each_entry_safe(sub, tmp, &sc->subscriptions, service_list) {
+		tipc_sub_report_overlap(sub, lower, upper, TIPC_WITHDRAWN,
+					p->port, node, p->scope, last);
+	}
 
 	/* Remove service range item if this was its last publication */
-	if (sr && list_empty(&sr->all_publ)) {
+	if (list_empty(&sr->all_publ)) {
 		rb_erase(&sr->tree_node, &sc->ranges);
 		kfree(sr);
 	}
@@ -396,6 +399,7 @@ struct publication *tipc_nametbl_remove_publ(struct net *net, u32 type,
 		hlist_del_init_rcu(&sc->service_list);
 		kfree_rcu(sc, rcu);
 	}
+exit:
 	spin_unlock_bh(&sc->lock);
 	return p;
 }
@@ -437,7 +441,7 @@ u32 tipc_nametbl_translate(struct net *net, u32 type, u32 instance, u32 *dnode)
 		goto not_found;
 
 	spin_lock_bh(&sc->lock);
-	sr = tipc_service_find_range(sc, instance);
+	sr = tipc_service_first_range(sc, instance);
 	if (unlikely(!sr))
 		goto no_match;
 
@@ -484,7 +488,7 @@ bool tipc_nametbl_lookup(struct net *net, u32 type, u32 instance, u32 scope,
 
 	spin_lock_bh(&sc->lock);
 
-	sr = tipc_service_find_range(sc, instance);
+	sr = tipc_service_first_range(sc, instance);
 	if (!sr)
 		goto no_match;
 
@@ -756,8 +760,7 @@ static void tipc_service_delete(struct net *net, struct tipc_service *sc)
 	spin_lock_bh(&sc->lock);
 	rbtree_postorder_for_each_entry_safe(sr, tmpr, &sc->ranges, tree_node) {
 		list_for_each_entry_safe(p, tmp, &sr->all_publ, all_publ) {
-			tipc_service_remove_publ(net, sc, p->lower, p->upper,
-						 p->node, p->key, &sr);
+			tipc_service_remove_publ(sr, p->node, p->key);
 			kfree_rcu(p, rcu);
 		}
 		rb_erase(&sr->tree_node, &sc->ranges);