[NET]: Fix fib_rules dump race

fib_rules_dump needs to use list_for_each_entry_rcu to protect against
concurrent changes to the rules list.
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/fib_rules.c

@@ -374,7 +374,7 @@ int fib_rules_dump(struct sk_buff *skb, struct netlink_callback *cb, int family)
 		return -EAFNOSUPPORT;
 
 	rcu_read_lock();
-	list_for_each_entry(rule, ops->rules_list, list) {
+	list_for_each_entry_rcu(rule, ops->rules_list, list) {
 		if (idx < cb->args[0])
 			goto skip;