rose: Add length checks to CALL_REQUEST parsing

Define some constant offsets for CALL_REQUEST based on the description
at <http://www.techfest.com/networking/wan/x25plp.htm> and the
definition of ROSE as using 10-digit (5-byte) addresses.  Use them
consistently.  Validate all implicit and explicit facilities lengths.
Validate the address length byte rather than either trusting or
assuming its value.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
static int rose_device_event(struct notifier_block *this, unsigned long event,
	void *ptr)
{
	struct net_device *dev = (struct net_device *)ptr;

	if (!net_eq(dev_net(dev), &init_net))
		return NOTIFY_DONE;

	if (event != NETDEV_DOWN)
		return NOTIFY_DONE;

	switch (dev->type) {
	case ARPHRD_ROSE:
		rose_kill_by_device(dev);
		break;
	case ARPHRD_AX25:
		rose_link_device_down(dev);
		rose_rt_device_down(dev);
		break;
	}

	return NOTIFY_DONE;
}

static int rose_device_event(struct notifier_block *this, unsigned long event,
	void *ptr)
{
	struct net_device *dev = (struct net_device *)ptr;

	if (!net_eq(dev_net(dev), &init_net))
		return NOTIFY_DONE;

	if (event != NETDEV_DOWN)
		return NOTIFY_DONE;

	switch (dev->type) {
	case ARPHRD_ROSE:
		rose_kill_by_device(dev);
		break;
	case ARPHRD_AX25:
		rose_link_device_down(dev);
		rose_rt_device_down(dev);
		break;
	}

	return NOTIFY_DONE;
}
