HID: hid-bigbenff: fix race condition for scheduled work during removal

It's possible that there is scheduled work left while the device is
already being removed, which can cause a kernel crash. Adding a flag
will avoid this.

Signed-off-by: Hanno Zulla <[e-mail]>
Signed-off-by: Benjamin Tissoires <[e-mail]>

drivers/hid/hid-bigbenff.c

···
 struct bigben_device {
 	struct hid_device *hid;
 	struct hid_report *report;
+	bool removed;
 	u8 led_state;         /* LED1 = 1 .. LED4 = 8 */
 	u8 right_motor_on;    /* right motor off/on 0/1 */
 	u8 left_motor_force;  /* left motor force 0-255 */
···
 	struct bigben_device *bigben = container_of(work,
 		struct bigben_device, worker);
 	struct hid_field *report_field = bigben->report->field[0];
+
+	if (bigben->removed)
+		return;
 
 	if (bigben->work_led) {
 		bigben->work_led = false;
···
 {
 	struct bigben_device *bigben = hid_get_drvdata(hid);
 
+	bigben->removed = true;
 	cancel_work_sync(&bigben->worker);
 	hid_hw_stop(hid);
 }
···
 		return -ENOMEM;
 	hid_set_drvdata(hid, bigben);
 	bigben->hid = hid;
+	bigben->removed = false;
 
 	error = hid_parse(hid);
 	if (error) {