[PATCH] HID: holtek: fix slab-out-of-bounds Write in holtek_kbd_input_event

[Ma Ke]

There is a slab-out-of-bounds Write bug in hid-holtek-kbd driver.
The problem is the driver assumes the device must have an input
but some malicious devices violate this assumption.

Fix this by checking hid_device's input is non-empty before its usage.

Signed-off-by: Ma Ke <make_ruc2021@xxxxxxx>
---
 drivers/hid/hid-holtek-kbd.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/hid/hid-holtek-kbd.c b/drivers/hid/hid-holtek-kbd.c
index 403506b9697e..b346d68a06f5 100644
--- a/drivers/hid/hid-holtek-kbd.c
+++ b/drivers/hid/hid-holtek-kbd.c
@@ -130,6 +130,10 @@ static int holtek_kbd_input_event(struct input_dev *dev, unsigned int type,
 		return -ENODEV;
 
 	boot_hid = usb_get_intfdata(boot_interface);
+	if (list_empty(&boot_hid->inputs)) {
+		hid_err(hid, "no inputs found\n");
+		return -ENODEV;
+	}
 	boot_hid_input = list_first_entry(&boot_hid->inputs,
 		struct hid_input, list);
 
-- 
2.37.2