HID: holtek: test for sanity of intfdata

The ioctl handler uses the intfdata of a second interface,
which may not be present in a broken or malicious device, hence
the intfdata needs to be checked for NULL.

[jkosina@suse.cz: fix newly added spurious space]
Reported-by: syzbot+965152643a75a56737be@syzkaller.appspotmail.com
Signed-off-by: Oliver Neukum <oneukum@suse.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-holtek-kbd.c

@@ -123,9 +123,14 @@ static int holtek_kbd_input_event(struct input_dev *dev, unsigned int type,
 
 	/* Locate the boot interface, to receive the LED change events */
 	struct usb_interface *boot_interface = usb_ifnum_to_if(usb_dev, 0);
+	struct hid_device *boot_hid;
+	struct hid_input *boot_hid_input;
 
-	struct hid_device *boot_hid = usb_get_intfdata(boot_interface);
-	struct hid_input *boot_hid_input = list_first_entry(&boot_hid->inputs,
+	if (unlikely(boot_interface == NULL))
+		return -ENODEV;
+
+	boot_hid = usb_get_intfdata(boot_interface);
+	boot_hid_input = list_first_entry(&boot_hid->inputs,
 		struct hid_input, list);
 
 	return boot_hid_input->input->event(boot_hid_input->input, type, code,