CVE-2026-46202: HID: appletb-kbd: run inactivity autodim from workqueues

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

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

HID: appletb-kbd: run inactivity autodim from workqueues

The autodim code in hid-appletb-kbd takes backlight_device->ops_lock
via backlight_device_set_brightness() -> mutex_lock() from two
different atomic contexts:

 * appletb_inactivity_timer() is a struct timer_list callback, so it
   runs in softirq context.  Every expiry triggers

     BUG: sleeping function called from invalid context at kernel/locking/mutex.c:591
     Call Trace:
      <IRQ>
      __might_resched
      __mutex_lock
      backlight_device_set_brightness
      appletb_inactivity_timer
      call_timer_fn
      run_timer_softirq

 * reset_inactivity_timer() is called from appletb_kbd_hid_event() and
   appletb_kbd_inp_event().  On real USB hardware these run in
   softirq/IRQ context (URB completion and input-event dispatch).
   When the Touch Bar has already been dimmed or turned off, the
   reset path calls backlight_device_set_brightness() directly to
   restore brightness, producing the same warning.

Both call sites hit the same mutex_lock()-from-atomic bug.  Fix them
together by moving the blocking work onto the system workqueue:

 * Convert the inactivity timer from struct timer_list to
   struct delayed_work; the callback (appletb_inactivity_work) now
   runs in process context where mutex_lock() is legal.
 * Add a dedicated struct work_struct restore_brightness_work and have
   reset_inactivity_timer() schedule it instead of calling
   backlight_device_set_brightness() directly.

Cancel both works synchronously during driver tear-down alongside the
existing backlight reference drop.

The semantics are unchanged (same delays, same state transitions on
dim, turn-off and user activity); only the execution context of the
sleeping call changes.  The timer field and callback are renamed to
match their new type; reset_inactivity_timer() keeps its name because
it is invoked from input event paths that read naturally as "reset
the inactivity timer".

The Linux kernel CVE team has assigned CVE-2026-46202 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.15 with commit 93a0fc48948107e0cc34e1de22c3cb363a8f2783 and fixed in 6.18.32 with commit 5c0830323689ef15224f0025276176988861b3b0
	Issue introduced in 6.15 with commit 93a0fc48948107e0cc34e1de22c3cb363a8f2783 and fixed in 7.0.9 with commit 2473a334c292af257ef68e33bc7760f4a8251812
	Issue introduced in 6.15 with commit 93a0fc48948107e0cc34e1de22c3cb363a8f2783 and fixed in 7.1-rc4 with commit 1654e53349d4e657b331de354313461f401f5063

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-46202
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/hid/hid-appletb-kbd.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/5c0830323689ef15224f0025276176988861b3b0
	https://git.kernel.org/stable/c/2473a334c292af257ef68e33bc7760f4a8251812
	https://git.kernel.org/stable/c/1654e53349d4e657b331de354313461f401f5063