1 files changed, 29 insertions, 9 deletions

diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index e31118f417b4..b7c4befe67ec 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -637,6 +637,11 @@ static struct fib6_node *fib6_add_1(struct net *net,
 			if (!(fn->fn_flags & RTN_RTINFO)) {
 				RCU_INIT_POINTER(fn->leaf, NULL);
 				rt6_release(leaf);
+			/* remove null_entry in the root node */
+			} else if (fn->fn_flags & RTN_TL_ROOT &&
+				   rcu_access_pointer(fn->leaf) ==
+				   net->ipv6.ip6_null_entry) {
+				RCU_INIT_POINTER(fn->leaf, NULL);
 			}
 
 			return fn;
@@ -1267,13 +1272,17 @@ out:
 	return err;
 
 failure:
-	/* fn->leaf could be NULL if fn is an intermediate node and we
-	 * failed to add the new route to it in both subtree creation
-	 * failure and fib6_add_rt2node() failure case.
-	 * In both cases, fib6_repair_tree() should be called to fix
-	 * fn->leaf.
+	/* fn->leaf could be NULL and fib6_repair_tree() needs to be called if:
+	 * 1. fn is an intermediate node and we failed to add the new
+	 * route to it in both subtree creation failure and fib6_add_rt2node()
+	 * failure case.
+	 * 2. fn is the root node in the table and we fail to add the first
+	 * default route to it.
 	 */
-	if (fn && !(fn->fn_flags & (RTN_RTINFO|RTN_ROOT)))
+	if (fn &&
+	    (!(fn->fn_flags & (RTN_RTINFO|RTN_ROOT)) ||
+	     (fn->fn_flags & RTN_TL_ROOT &&
+	      !rcu_access_pointer(fn->leaf))))
 		fib6_repair_tree(info->nl_net, table, fn);
 	/* Always release dst as dst->__refcnt is guaranteed
 	 * to be taken before entering this function
@@ -1528,6 +1537,12 @@ static struct fib6_node *fib6_repair_tree(struct net *net,
 	struct fib6_walker *w;
 	int iter = 0;
 
+	/* Set fn->leaf to null_entry for root node. */
+	if (fn->fn_flags & RTN_TL_ROOT) {
+		rcu_assign_pointer(fn->leaf, net->ipv6.ip6_null_entry);
+		return fn;
+	}
+
 	for (;;) {
 		struct fib6_node *fn_r = rcu_dereference_protected(fn->right,
 					    lockdep_is_held(&table->tb6_lock));
@@ -1683,10 +1698,15 @@ static void fib6_del_route(struct fib6_table *table, struct fib6_node *fn,
 	}
 	read_unlock(&net->ipv6.fib6_walker_lock);
 
-	/* If it was last route, expunge its radix tree node */
+	/* If it was last route, call fib6_repair_tree() to:
+	 * 1. For root node, put back null_entry as how the table was created.
+	 * 2. For other nodes, expunge its radix tree node.
+	 */
 	if (!rcu_access_pointer(fn->leaf)) {
-		fn->fn_flags &= ~RTN_RTINFO;
-		net->ipv6.rt6_stats->fib_route_nodes--;
+		if (!(fn->fn_flags & RTN_TL_ROOT)) {
+			fn->fn_flags &= ~RTN_RTINFO;
+			net->ipv6.rt6_stats->fib_route_nodes--;
+		}
 		fn = fib6_repair_tree(net, table, fn);
 	}