staging: comedi: fix infoleak to userspace

driver_name and board_name are pointers to strings, not buffers of size
COMEDI_NAMELEN.  Copying COMEDI_NAMELEN bytes of a string containing
less than COMEDI_NAMELEN-1 bytes would leak some unrelated bytes.

Signed-off-by: Vasiliy Kulikov <segoon@openwall.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
static int do_cancel(struct comedi_device *dev, struct comedi_subdevice *s)
{
	int ret = 0;

	if ((comedi_get_subdevice_runflags(s) & SRF_RUNNING) && s->cancel)
		ret = s->cancel(dev, s);

	do_become_nonbusy(dev, s);

	return ret;
}

static int do_cancel(struct comedi_device *dev, struct comedi_subdevice *s)
{
	int ret = 0;

	if ((comedi_get_subdevice_runflags(s) & SRF_RUNNING) && s->cancel)
		ret = s->cancel(dev, s);

	do_become_nonbusy(dev, s);

	return ret;
}
