In the Linux kernel, the following vulnerability has been resolved: HID: appletb-kbd: run...

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".