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

Greg KH
2025-11-25T11:44:05Z

On Tue, Nov 25, 2025 at 06:36:27PM +0800, Duoming Zhou wrote:
> 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>
> ---
> 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
>
>

What changed from v1?