[BUG] general protection fault in input_unregister_device

[Xianying Wang <wangxianying546@gmail.com>]

Hi,

I discovered a kernel crash described as "general protection fault in
input_unregister_device." The crash occurs in the input subsystem,
specifically in the function input_unregister_device
(drivers/input/input.c:2500), due to dereferencing a non-canonical
address, resulting in a general protection fault.

According to the crash report, the faulting address is
0xdffffc00000000a4, which corresponds to a KASAN shadow memory region.
The crash is triggered when mac_hid_toggle_emumouse calls
mac_hid_stop_emulation, which in turn invokes
mac_hid_destroy_emumouse, eventually leading to a call to
input_unregister_device with an invalid or uninitialized input_dev
pointer.

The report indicates that a corrupted or NULL input_dev structure was
passed into input_unregister_device, possibly due to a use-after-free,
double unregister, or incomplete initialization in the emumouse path
in mac_hid.

This can be reproduced on:

HEAD commit:

commit adc218676eef25575469234709c2d87185ca223a

report: https://pastebin.com/raw/4TeX6E8M

console output : https://pastebin.com/raw/ZE2AZ1Gq

kernel config : https://pastebin.com/raw/BpCtvUt2

C reproducer :

part1：https://pastebin.com/raw/jhU9v99k

part2：https://pastebin.com/raw/dcaKCHZ1

part3：https://pastebin.com/raw/CzgGBb7C

part4：https://pastebin.com/raw/MnwtYcjd

part5：https://pastebin.com/raw/VE8xNmHT

Best regards,

Xianying