veth: Enforce minimum size of VETH_INFO_PEER

VETH_INFO_PEER carries struct ifinfomsg plus optional IFLA
attributes. A minimal size of sizeof(struct ifinfomsg) must be
enforced or we may risk accessing that struct beyond the limits
of the netlink message.
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/veth.c

@@ -422,7 +422,9 @@ static void veth_dellink(struct net_device *dev, struct list_head *head)
 	unregister_netdevice_queue(peer, head);
 }
 
-static const struct nla_policy veth_policy[VETH_INFO_MAX + 1];
+static const struct nla_policy veth_policy[VETH_INFO_MAX + 1] = {
+	[VETH_INFO_PEER]	= { .len = sizeof(struct ifinfomsg) },
+};
 
 static struct rtnl_link_ops veth_link_ops = {
 	.kind		= DRV_NAME,