selinux: ensure we cleanup the internal AVC counters on error in avc_insert()

Fix avc_insert() to call avc_node_kill() if we've already allocated
an AVC node and the code fails to insert the node in the cache.

Fixes: fa1aa143 ("selinux: extended permissions for ioctls")
Reported-by: rsiddoji@codeaurora.org
Suggested-by: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/selinux/avc.c

@@ -617,40 +617,37 @@ static struct avc_node *avc_insert(struct selinux_avc *avc,
 	struct avc_node *pos, *node = NULL;
 	int hvalue;
 	unsigned long flag;
+	spinlock_t *lock;
+	struct hlist_head *head;
 
 	if (avc_latest_notif_update(avc, avd->seqno, 1))
-		goto out;
+		return NULL;
 
 	node = avc_alloc_node(avc);
-	if (node) {
-		struct hlist_head *head;
-		spinlock_t *lock;
-		int rc = 0;
-
-		hvalue = avc_hash(ssid, tsid, tclass);
-		avc_node_populate(node, ssid, tsid, tclass, avd);
-		rc = avc_xperms_populate(node, xp_node);
-		if (rc) {
-			kmem_cache_free(avc_node_cachep, node);
-			return NULL;
-		}
-		head = &avc->avc_cache.slots[hvalue];
-		lock = &avc->avc_cache.slots_lock[hvalue];
+	if (!node)
+		return NULL;
 
-		spin_lock_irqsave(lock, flag);
-		hlist_for_each_entry(pos, head, list) {
-			if (pos->ae.ssid == ssid &&
-			    pos->ae.tsid == tsid &&
-			    pos->ae.tclass == tclass) {
-				avc_node_replace(avc, node, pos);
-				goto found;
-			}
+	avc_node_populate(node, ssid, tsid, tclass, avd);
+	if (avc_xperms_populate(node, xp_node)) {
+		avc_node_kill(avc, node);
+		return NULL;
+	}
+
+	hvalue = avc_hash(ssid, tsid, tclass);
+	head = &avc->avc_cache.slots[hvalue];
+	lock = &avc->avc_cache.slots_lock[hvalue];
+	spin_lock_irqsave(lock, flag);
+	hlist_for_each_entry(pos, head, list) {
+		if (pos->ae.ssid == ssid &&
+			pos->ae.tsid == tsid &&
+			pos->ae.tclass == tclass) {
+			avc_node_replace(avc, node, pos);
+			goto found;
 		}
-		hlist_add_head_rcu(&node->list, head);
-found:
-		spin_unlock_irqrestore(lock, flag);
 	}
-out:
+	hlist_add_head_rcu(&node->list, head);
+found:
+	spin_unlock_irqrestore(lock, flag);
 	return node;
 }