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Message-ID: <2025072504-CVE-2025-38378-4e10@gregkh>
Date: Fri, 25 Jul 2025 14:55:09 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-38378: HID: appletb-kbd: fix slab use-after-free bug in appletb_kbd_probe

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

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

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

HID: appletb-kbd: fix slab use-after-free bug in appletb_kbd_probe

In probe appletb_kbd_probe() a "struct appletb_kbd *kbd" is allocated
via devm_kzalloc() to store touch bar keyboard related data.
Later on if backlight_device_get_by_name() finds a backlight device
with name "appletb_backlight" a timer (kbd->inactivity_timer) is setup
with appletb_inactivity_timer() and the timer is armed to run after
appletb_tb_dim_timeout (60) seconds.

A use-after-free is triggered when failure occurs after the timer is
armed. This ultimately means probe failure occurs and as a result the
"struct appletb_kbd *kbd" which is device managed memory is freed.
After 60 seconds the timer will have expired and __run_timers will
attempt to access the timer (kbd->inactivity_timer) however the kdb
structure has been freed causing a use-after free.

[   71.636938] ==================================================================
[   71.637915] BUG: KASAN: slab-use-after-free in __run_timers+0x7ad/0x890
[   71.637915] Write of size 8 at addr ffff8881178c5958 by task swapper/1/0
[   71.637915]
[   71.637915] CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Not tainted 6.16.0-rc2-00318-g739a6c93cc75-dirty #12 PREEMPT(voluntary)
[   71.637915] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
[   71.637915] Call Trace:
[   71.637915]  <IRQ>
[   71.637915]  dump_stack_lvl+0x53/0x70
[   71.637915]  print_report+0xce/0x670
[   71.637915]  ? __run_timers+0x7ad/0x890
[   71.637915]  kasan_report+0xce/0x100
[   71.637915]  ? __run_timers+0x7ad/0x890
[   71.637915]  __run_timers+0x7ad/0x890
[   71.637915]  ? __pfx___run_timers+0x10/0x10
[   71.637915]  ? update_process_times+0xfc/0x190
[   71.637915]  ? __pfx_update_process_times+0x10/0x10
[   71.637915]  ? _raw_spin_lock_irq+0x80/0xe0
[   71.637915]  ? _raw_spin_lock_irq+0x80/0xe0
[   71.637915]  ? __pfx__raw_spin_lock_irq+0x10/0x10
[   71.637915]  run_timer_softirq+0x141/0x240
[   71.637915]  ? __pfx_run_timer_softirq+0x10/0x10
[   71.637915]  ? __pfx___hrtimer_run_queues+0x10/0x10
[   71.637915]  ? kvm_clock_get_cycles+0x18/0x30
[   71.637915]  ? ktime_get+0x60/0x140
[   71.637915]  handle_softirqs+0x1b8/0x5c0
[   71.637915]  ? __pfx_handle_softirqs+0x10/0x10
[   71.637915]  irq_exit_rcu+0xaf/0xe0
[   71.637915]  sysvec_apic_timer_interrupt+0x6c/0x80
[   71.637915]  </IRQ>
[   71.637915]
[   71.637915] Allocated by task 39:
[   71.637915]  kasan_save_stack+0x33/0x60
[   71.637915]  kasan_save_track+0x14/0x30
[   71.637915]  __kasan_kmalloc+0x8f/0xa0
[   71.637915]  __kmalloc_node_track_caller_noprof+0x195/0x420
[   71.637915]  devm_kmalloc+0x74/0x1e0
[   71.637915]  appletb_kbd_probe+0x37/0x3c0
[   71.637915]  hid_device_probe+0x2d1/0x680
[   71.637915]  really_probe+0x1c3/0x690
[   71.637915]  __driver_probe_device+0x247/0x300
[   71.637915]  driver_probe_device+0x49/0x210
[...]
[   71.637915]
[   71.637915] Freed by task 39:
[   71.637915]  kasan_save_stack+0x33/0x60
[   71.637915]  kasan_save_track+0x14/0x30
[   71.637915]  kasan_save_free_info+0x3b/0x60
[   71.637915]  __kasan_slab_free+0x37/0x50
[   71.637915]  kfree+0xcf/0x360
[   71.637915]  devres_release_group+0x1f8/0x3c0
[   71.637915]  hid_device_probe+0x315/0x680
[   71.637915]  really_probe+0x1c3/0x690
[   71.637915]  __driver_probe_device+0x247/0x300
[   71.637915]  driver_probe_device+0x49/0x210
[...]

The root cause of the issue is that the timer is not disarmed
on failure paths leading to it remaining active and accessing
freed memory. To fix this call timer_delete_sync() to deactivate
the timer.

Another small issue is that timer_delete_sync is called
unconditionally in appletb_kbd_remove(), fix this by checking
for a valid kbd->backlight_dev before calling timer_delete_sync.

The Linux kernel CVE team has assigned CVE-2025-38378 to this issue.


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

	Issue introduced in 6.15 with commit 93a0fc48948107e0cc34e1de22c3cb363a8f2783 and fixed in 6.15.6 with commit 51720dee3a61ebace36c3dcdd0b4a488e0970f29
	Issue introduced in 6.15 with commit 93a0fc48948107e0cc34e1de22c3cb363a8f2783 and fixed in 6.16-rc5 with commit 38224c472a038fa9ccd4085511dd9f3d6119dbf9

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-2025-38378
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/51720dee3a61ebace36c3dcdd0b4a488e0970f29
	https://git.kernel.org/stable/c/38224c472a038fa9ccd4085511dd9f3d6119dbf9

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