USB: hso: Fix OOB memory access in hso_probe/hso_get_config_data

The function hso_probe reads if_num from the USB device (as an u8) and uses
it without a length check to index an array, resulting in an OOB memory read
in hso_probe or hso_get_config_data.

Add a length check for both locations and updated hso_probe to bail on
error.

This issue has been assigned CVE-2018-19985.

Reported-by: Hui Peng <benquike@gmail.com>
Reported-by: Mathias Payer <mathias.payer@nebelwelt.net>
Signed-off-by: Hui Peng <benquike@gmail.com>
Signed-off-by: Mathias Payer <mathias.payer@nebelwelt.net>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
