Re: [PATCH v2 2/2] usb: typec: ucsi: fix use-after-free caused by uec->work

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

Tue, Nov 25, 2025 at 06:36:27PM +0800, Duoming Zhou kirjoitti:
> The delayed work uec->work is scheduled in gaokun_ucsi_probe()
> but never properly canceled in gaokun_ucsi_remove(). This creates
> use-after-free scenarios where the ucsi and gaokun_ucsi structure
> are freed after ucsi_destroy() completes execution, while the
> gaokun_ucsi_register_worker() might be either currently executing
> or still pending in the work queue. The already-freed gaokun_ucsi
> or ucsi structure may then be accessed.
> 
> Furthermore, the race window is 3 seconds, which is sufficiently
> long to make this bug easily reproducible. The following is the
> trace captured by KASAN:
> 
> ==================================================================
> BUG: KASAN: slab-use-after-free in __run_timers+0x5ec/0x630
> Write of size 8 at addr ffff00000ec28cc8 by task swapper/0/0
> ...
> Call trace:
>  show_stack+0x18/0x24 (C)
>  dump_stack_lvl+0x78/0x90
>  print_report+0x114/0x580
>  kasan_report+0xa4/0xf0
>  __asan_report_store8_noabort+0x20/0x2c
>  __run_timers+0x5ec/0x630
>  run_timer_softirq+0xe8/0x1cc
>  handle_softirqs+0x294/0x720
>  __do_softirq+0x14/0x20
>  ____do_softirq+0x10/0x1c
>  call_on_irq_stack+0x30/0x48
>  do_softirq_own_stack+0x1c/0x28
>  __irq_exit_rcu+0x27c/0x364
>  irq_exit_rcu+0x10/0x1c
>  el1_interrupt+0x40/0x60
>  el1h_64_irq_handler+0x18/0x24
>  el1h_64_irq+0x6c/0x70
>  arch_local_irq_enable+0x4/0x8 (P)
>  do_idle+0x334/0x458
>  cpu_startup_entry+0x60/0x70
>  rest_init+0x158/0x174
>  start_kernel+0x2f8/0x394
>  __primary_switched+0x8c/0x94
> 
> Allocated by task 72 on cpu 0 at 27.510341s:
>  kasan_save_stack+0x2c/0x54
>  kasan_save_track+0x24/0x5c
>  kasan_save_alloc_info+0x40/0x54
>  __kasan_kmalloc+0xa0/0xb8
>  __kmalloc_node_track_caller_noprof+0x1c0/0x588
>  devm_kmalloc+0x7c/0x1c8
>  gaokun_ucsi_probe+0xa0/0x840  auxiliary_bus_probe+0x94/0xf8
>  really_probe+0x17c/0x5b8
>  __driver_probe_device+0x158/0x2c4
>  driver_probe_device+0x10c/0x264
>  __device_attach_driver+0x168/0x2d0
>  bus_for_each_drv+0x100/0x188
>  __device_attach+0x174/0x368
>  device_initial_probe+0x14/0x20
>  bus_probe_device+0x120/0x150
>  device_add+0xb3c/0x10fc
>  __auxiliary_device_add+0x88/0x130
> ...
> 
> Freed by task 73 on cpu 1 at 28.910627s:
>  kasan_save_stack+0x2c/0x54
>  kasan_save_track+0x24/0x5c
>  __kasan_save_free_info+0x4c/0x74
>  __kasan_slab_free+0x60/0x8c
>  kfree+0xd4/0x410
>  devres_release_all+0x140/0x1f0
>  device_unbind_cleanup+0x20/0x190
>  device_release_driver_internal+0x344/0x460
>  device_release_driver+0x18/0x24
>  bus_remove_device+0x198/0x274
>  device_del+0x310/0xa84
> ...
> 
> The buggy address belongs to the object at ffff00000ec28c00
>  which belongs to the cache kmalloc-512 of size 512
> The buggy address is located 200 bytes inside of
>  freed 512-byte region
> The buggy address belongs to the physical page:
> page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4ec28
> head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
> flags: 0x3fffe0000000040(head|node=0|zone=0|lastcpupid=0x1ffff)
> page_type: f5(slab)
> raw: 03fffe0000000040 ffff000008801c80 dead000000000122 0000000000000000
> raw: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000
> head: 03fffe0000000040 ffff000008801c80 dead000000000122 0000000000000000
> head: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000
> head: 03fffe0000000002 fffffdffc03b0a01 00000000ffffffff 00000000ffffffff
> head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000004
> page dumped because: kasan: bad access detected
> 
> Memory state around the buggy address:
>  ffff00000ec28b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>  ffff00000ec28c00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >ffff00000ec28c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                                               ^
>  ffff00000ec28d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff00000ec28d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
> 
> Add disable_delayed_work_sync() in gaokun_ucsi_remove() to ensure
> that uec->work is properly canceled and prevented from executing
> after the ucsi and gaokun_ucsi structure have been deallocated.
> 
> Fixes: 00327d7f2c8c ("usb: typec: ucsi: add Huawei Matebook E Go ucsi driver")
> Cc: stable@vger.kernel.org
> Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>

Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

> ---
>  drivers/usb/typec/ucsi/ucsi_huawei_gaokun.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/usb/typec/ucsi/ucsi_huawei_gaokun.c b/drivers/usb/typec/ucsi/ucsi_huawei_gaokun.c
> index 8401ab414bd..c5965656bab 100644
> --- a/drivers/usb/typec/ucsi/ucsi_huawei_gaokun.c
> +++ b/drivers/usb/typec/ucsi/ucsi_huawei_gaokun.c
> @@ -503,6 +503,7 @@ static void gaokun_ucsi_remove(struct auxiliary_device *adev)
>  {
>  	struct gaokun_ucsi *uec = auxiliary_get_drvdata(adev);
>  
> +	disable_delayed_work_sync(&uec->work);
>  	gaokun_ec_unregister_notify(uec->ec, &uec->nb);
>  	ucsi_unregister(uec->ucsi);
>  	ucsi_destroy(uec->ucsi);
> -- 
> 2.34.1

-- 
heikki