static struct hid_field *hid_register_field(struct hid_report *report, unsigned usages, unsigned values)
{
	struct hid_field *field;

	if (report->maxfield == HID_MAX_FIELDS) {
		hid_err(report->device, "too many fields in report\n");
		return NULL;
	}

	field = kzalloc((sizeof(struct hid_field) +
			 usages * sizeof(struct hid_usage) +
			 values * sizeof(unsigned)), GFP_KERNEL);
	if (!field)
		return NULL;

	field->index = report->maxfield++;
	report->field[field->index] = field;
	field->usage = (struct hid_usage *)(field + 1);
	field->value = (s32 *)(field->usage + usages);
	field->report = report;

	return field;
}

The product reads data past the end, or before the beginning, of the intended buffer.