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.

Affected Software

References

• https://git.kernel.org/stable/c/17f5928d7010bc9e002930326b59e60e40c09ee3
• https://git.kernel.org/stable/c/2bb6e7143cf70ed281822d26c1848b2897ac36e9
• https://git.kernel.org/stable/c/3eca1a8165b5e7996e699e9df76cb4645e184d42
• https://git.kernel.org/stable/c/46c8beeccd8ab2c863827254a85ea877654a3534
• https://git.kernel.org/stable/c/523db788c0f84612707638e266e8957ca7e3a756
• https://git.kernel.org/stable/c/df3d8aa1a9392da3de66398e7a03422463806b21