CVE-2025-38016 Information

Description

In the Linux kernel the following vulnerability has been resolved:

HID: bpf: abort dispatch if device destroyed

The current HID bpf implementation assumes no output report/request will go through it after hid_bpf_destroy_device() has been called. This leads to a bug that unplugging certain types of HID devices causes a cleaned- up SRCU to be accessed. The bug was previously a hidden failure until a recent x86 percpu change [1] made it access not-present pages.

The bug will be triggered if the conditions below are met:

A) a device under the driver has some LEDs on B) hid_ll_driver->request() is uninplemented (e.g. logitech-djreceiver)

If condition A is met hidinput_led_worker() is always scheduled after hid_bpf_destroy_device().

hid_destroy_device hid_bpf_destroy_device cleanup_srcu_struct(&hdev->bpf.srcu) hid_remove_device … led_classdev_unregister led_trigger_set(led_cdev NULL) led_set_brightness(led_cdev LED_OFF) … input_inject_event input_event_dispose hidinput_input_event schedule_work(&hid->led_work) [hidinput_led_worker]

This is fine when condition B is not met where hidinput_led_worker() calls hid_ll_driver->request(). This is the case for most HID drivers which implement it or use the generic one from usbhid. The driver itself or an underlying driver will then abort processing the request.

Otherwise hidinput_led_worker() tries hid_hw_output_report() and leads to the bug.

hidinput_led_worker hid_hw_output_report dispatch_hid_bpf_output_report srcu_read_lock(&hdev->bpf.srcu) srcu_read_unlock(&hdev->bpf.srcu idx)

The bug has existed since the introduction [2] of dispatch_hid_bpf_output_report(). However the same bug also exists in dispatch_hid_bpf_raw_requests() and I’ve reproduced (no visible effect because of the lack of [1] but confirmed bpf.destroyed == 1) the bug against the commit (i.e. the Fixes:) introducing the function. This is because hidinput_led_worker() falls back to hid_hw_raw_request() when hid_ll_driver->output_report() is uninplemented (e.g. logitech- djreceiver).

hidinput_led_worker hid_hw_output_report: -ENOSYS hid_hw_raw_request dispatch_hid_bpf_raw_requests srcu_read_lock(&hdev->bpf.srcu) ` srcu_read_unlock(&hdev->bpf.srcu idx)

Fix the issue by returning early in the two mentioned functions if hid_bpf has been marked as destroyed. Though dispatch_hid_bpf_device_event() handles input events and there is no evidence that it may be called after the destruction the same check as a safety net is also added to it to maintain the consistency among all dispatch functions.

The impact of the bug on other architectures is unclear. Even if it acts as a hidden failure this is still dangerous because it corrupts whatever is on the address calculated by SRCU. Thus CC’ing the stable list.

[1]: commit 9d7de2aa8b41 (�/percpu/64: Use relative percpu offsets) [2]: commit 9286675a2aed (\HID: bpf: add HID-BPF hooks for hid_hw_output_report)

Reference

https://git.kernel.org/stable/c/578e1b96fad7402ff7e9c7648c8f1ad0225147c8 https://git.kernel.org/stable/c/e4b4fe25a4101d1ddb5884f40e149a3618983b66 https://git.kernel.org/stable/c/f8544be7e8e55b0ef23e1ab90e23e8d4d4aad3d3