The powermate driver expects at least one valid USB endpoint in its
probe function.  If given malicious descriptors that specify 0 for
the number of endpoints, it will crash.  Validate the number of
endpoints on the interface before using them.

The full report for this issue can be found here:
http://seclists.org/bugtraq/2016/Mar/85Reported-by: NRalf Spenneberg <ralf@spenneberg.net>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: NJosh Boyer <jwboyer@fedoraproject.org>
Signed-off-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>