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

duoming
2025-11-25T12:02:48Z

On Tue, 25 Nov 2025 12:44:02 +0100, Greg KH 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?

The original patch[1] only fixes the probe failure in
gaokun_ucsi_probe(). This new version is a patch series
that also addresses the use-after-free issue.

[1] https://lore.kernel.org/lkml/20251125082505.52249-1-duoming@zju.edu.cn/