HID: usbhid: free raw_report buffers in usbhid_stop

Free the unsent raw_report buffers when the device is removed.

Fixes a memory leak reported by syzbot at:
https://syzkaller.appspot.com/bug?id=7b4fa7cb1a7c2d3342a2a8a6c53371c8c418ab47

Reported-by: syzbot+47b26cd837ececfc666d@syzkaller.appspotmail.com
Tested-by: syzbot+47b26cd837ececfc666d@syzkaller.appspotmail.com
Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

Author: anirudhrb

drivers/hid/usbhid/hid-core.c

@@ -505,7 +505,7 @@ static void hid_ctrl(struct urb *urb)
 
 	if (unplug) {
 		usbhid->ctrltail = usbhid->ctrlhead;
-	} else {
+	} else if (usbhid->ctrlhead != usbhid->ctrltail) {
 		usbhid->ctrltail = (usbhid->ctrltail + 1) & (HID_CONTROL_FIFO_SIZE - 1);
 
 		if (usbhid->ctrlhead != usbhid->ctrltail &&
@@ -1223,9 +1223,20 @@ static void usbhid_stop(struct hid_device *hid)
 	mutex_lock(&usbhid->mutex);
 
 	clear_bit(HID_STARTED, &usbhid->iofl);
+
 	spin_lock_irq(&usbhid->lock);	/* Sync with error and led handlers */
 	set_bit(HID_DISCONNECTED, &usbhid->iofl);
+	while (usbhid->ctrltail != usbhid->ctrlhead) {
+		if (usbhid->ctrl[usbhid->ctrltail].dir == USB_DIR_OUT) {
+			kfree(usbhid->ctrl[usbhid->ctrltail].raw_report);
+			usbhid->ctrl[usbhid->ctrltail].raw_report = NULL;
+		}
+
+		usbhid->ctrltail = (usbhid->ctrltail + 1) &
+			(HID_CONTROL_FIFO_SIZE - 1);
+	}
 	spin_unlock_irq(&usbhid->lock);
+
 	usb_kill_urb(usbhid->urbin);
 	usb_kill_urb(usbhid->urbout);
 	usb_kill_urb(usbhid->urbctrl);