dcbnl: fix various netlink info leaks

The dcb netlink interface leaks stack memory in various places:
* perm_addr[] buffer is only filled at max with 12 of the 32 bytes but
  copied completely,
* no in-kernel driver fills all fields of an IEEE 802.1Qaz subcommand,
  so we're leaking up to 58 bytes for ieee_ets structs, up to 136 bytes
  for ieee_pfc structs, etc.,
* the same is true for CEE -- no in-kernel driver fills the whole
  struct,

Prevent all of the above stack info leaks by properly initializing the
buffers/structures involved.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
static int dcbnl_getdcbx(struct net_device *netdev, struct nlmsghdr *nlh,
			 u32 seq, struct nlattr **tb, struct sk_buff *skb)
{
	if (!netdev->dcbnl_ops->getdcbx)
		return -EOPNOTSUPP;

	return nla_put_u8(skb, DCB_ATTR_DCBX,
			  netdev->dcbnl_ops->getdcbx(netdev));
}

static int dcbnl_getdcbx(struct net_device *netdev, struct nlmsghdr *nlh,
			 u32 seq, struct nlattr **tb, struct sk_buff *skb)
{
	if (!netdev->dcbnl_ops->getdcbx)
		return -EOPNOTSUPP;

	return nla_put_u8(skb, DCB_ATTR_DCBX,
			  netdev->dcbnl_ops->getdcbx(netdev));
}
