ipv6: Initialize the struct rt6_info behind the dst_enty field

We start initializing the struct rt6_info at the first field
behind the struct dst_enty. This is error prone because it
might leave a new field uninitialized. So start initializing
the struct rt6_info right behind the dst_entry.
Suggested-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/route.c

@@ -280,8 +280,9 @@ static inline struct rt6_info *ip6_dst_alloc(struct net *net,
 					0, 0, flags);
 
 	if (rt) {
-		memset(&rt->n, 0,
-		       sizeof(*rt) - sizeof(struct dst_entry));
+		struct dst_entry *dst = &rt->dst;
+
+		memset(dst + 1, 0, sizeof(*rt) - sizeof(*dst));
 		rt6_init_peer(rt, table ? &table->tb6_peers : net->ipv6.peers);
 	}
 	return rt;
@@ -982,11 +983,11 @@ struct dst_entry *ip6_blackhole_route(struct net *net, struct dst_entry *dst_ori
 
 	rt = dst_alloc(&ip6_dst_blackhole_ops, ort->dst.dev, 1, 0, 0);
 	if (rt) {
-		memset(&rt->rt6i_table, 0, sizeof(*rt) - sizeof(struct dst_entry));
-		rt6_init_peer(rt, net->ipv6.peers);
-
 		new = &rt->dst;
 
+		memset(new + 1, 0, sizeof(*rt) - sizeof(*new));
+		rt6_init_peer(rt, net->ipv6.peers);
+
 		new->__use = 1;
 		new->input = dst_discard;
 		new->output = dst_discard;