CVE-2026-64365

In the Linux kernel, the following vulnerability has been resolved:

HID: letsketch: fix UAF on inrange_timer at driver unbind

letsketch_driver does not provide a .remove callback, but

letsketch_probe() arms a per-device timer:

timer_setup(&data->inrange_timer, letsketch_inrange_timeout, 0);

The timer is re-armed from letsketch_raw_event() with a 100 ms

timeout on every pen-in-range report, and its callback dereferences

data->input_tablet to deliver a synthetic BTN_TOOL_PEN release.

letsketch_data is allocated with devm_kzalloc(), and its input_dev

fields are devm-allocated via letsketch_setup_input_tablet(). On

device unbind (USB unplug or rmmod), the HID core runs its default

teardown and devm cleanup frees both letsketch_data and the input

devices. Because no .remove callback exists, nothing drains the

timer first: if raw_event armed it within ~100 ms of the unbind,

the pending timer fires on freed memory. This is a UAF read of

data and of data->input_tablet, followed by input_report_key() /

input_sync() into the freed input_dev.

The same problem can occur on the probe error path: if

hid_hw_start() enabled I/O on an always-poll-quirk device and then

failed, raw_event may have armed the timer before devm releases

data.

Fix by adding a .remove callback that calls hid_hw_stop() first.

hid_hw_stop() synchronously kills the URBs that deliver raw_event(),

so once it returns no path can re-arm the timer. timer_shutdown_sync()

then drains any in-flight callback and permanently disables further

mod_timer() calls. Apply the same timer_shutdown_sync() in the probe

error path so the timer is guaranteed not to outlive data.