* [PATCH v2] HID: appletb-kbd: fix slab use-after-free bug in appletb_kbd_probe
@ 2025-06-24 12:52 Qasim Ijaz
2025-06-24 13:11 ` Aditya Garg
2025-07-03 9:35 ` Jiri Kosina
0 siblings, 2 replies; 3+ messages in thread
From: Qasim Ijaz @ 2025-06-24 12:52 UTC (permalink / raw)
To: jikos, bentiss, gargaditya08; +Cc: linux-input, linux-kernel, stable
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.
Fixes: 93a0fc489481 ("HID: hid-appletb-kbd: add support for automatic brightness control while using the touchbar")
Cc: stable@vger.kernel.org
Signed-off-by: Qasim Ijaz <qasdev00@gmail.com>
---
v2:
- Add backlight check in remove() since we don't want to unconditionally call timer_delete_sync
drivers/hid/hid-appletb-kbd.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/drivers/hid/hid-appletb-kbd.c b/drivers/hid/hid-appletb-kbd.c
index e06567886e50..d11c49665147 100644
--- a/drivers/hid/hid-appletb-kbd.c
+++ b/drivers/hid/hid-appletb-kbd.c
@@ -438,8 +438,10 @@ static int appletb_kbd_probe(struct hid_device *hdev, const struct hid_device_id
return 0;
close_hw:
- if (kbd->backlight_dev)
+ if (kbd->backlight_dev) {
put_device(&kbd->backlight_dev->dev);
+ timer_delete_sync(&kbd->inactivity_timer);
+ }
hid_hw_close(hdev);
stop_hw:
hid_hw_stop(hdev);
@@ -453,10 +455,10 @@ static void appletb_kbd_remove(struct hid_device *hdev)
appletb_kbd_set_mode(kbd, APPLETB_KBD_MODE_OFF);
input_unregister_handler(&kbd->inp_handler);
- timer_delete_sync(&kbd->inactivity_timer);
-
- if (kbd->backlight_dev)
+ if (kbd->backlight_dev) {
put_device(&kbd->backlight_dev->dev);
+ timer_delete_sync(&kbd->inactivity_timer);
+ }
hid_hw_close(hdev);
hid_hw_stop(hdev);
--
2.39.5
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2] HID: appletb-kbd: fix slab use-after-free bug in appletb_kbd_probe
2025-06-24 12:52 [PATCH v2] HID: appletb-kbd: fix slab use-after-free bug in appletb_kbd_probe Qasim Ijaz
@ 2025-06-24 13:11 ` Aditya Garg
2025-07-03 9:35 ` Jiri Kosina
1 sibling, 0 replies; 3+ messages in thread
From: Aditya Garg @ 2025-06-24 13:11 UTC (permalink / raw)
To: Qasim Ijaz, jikos, bentiss; +Cc: linux-input, linux-kernel, stable
On 24/06/25 6:22 pm, Qasim Ijaz wrote:
> 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.
>
> Fixes: 93a0fc489481 ("HID: hid-appletb-kbd: add support for automatic brightness control while using the touchbar")
> Cc: stable@vger.kernel.org
> Signed-off-by: Qasim Ijaz <qasdev00@gmail.com>
Reviewed-by: Aditya Garg <gargaditya08@live.com>
> ---
> v2:
> - Add backlight check in remove() since we don't want to unconditionally call timer_delete_sync
>
> drivers/hid/hid-appletb-kbd.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] HID: appletb-kbd: fix slab use-after-free bug in appletb_kbd_probe
2025-06-24 12:52 [PATCH v2] HID: appletb-kbd: fix slab use-after-free bug in appletb_kbd_probe Qasim Ijaz
2025-06-24 13:11 ` Aditya Garg
@ 2025-07-03 9:35 ` Jiri Kosina
1 sibling, 0 replies; 3+ messages in thread
From: Jiri Kosina @ 2025-07-03 9:35 UTC (permalink / raw)
To: Qasim Ijaz; +Cc: bentiss, gargaditya08, linux-input, linux-kernel, stable
On Tue, 24 Jun 2025, Qasim Ijaz wrote:
> 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.
Thanks for reminding me of this one in the other thread. Now applied to
hid.git#for-6.16/upstream-fixes.
--
Jiri Kosina
SUSE Labs
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2025-07-03 9:35 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
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2025-06-24 12:52 [PATCH v2] HID: appletb-kbd: fix slab use-after-free bug in appletb_kbd_probe Qasim Ijaz
2025-06-24 13:11 ` Aditya Garg
2025-07-03 9:35 ` Jiri Kosina
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