Re: [PATCH] usb: core: port: Deattach Type-C connector on component unbind

[AceLan Kao]

Chia-Lin Kao (AceLan) <acelan.kao@xxxxxxxxxxxxx> 於 2026年6月11日週四 下午3:12寫道：
>
> connector_unbind() is the mirror of connector_bind(), but it is missing
> the symmetric call to typec_deattach() that connector_bind() makes via:
>
>     if (port_dev->child)
>         typec_attach(port_dev->connector, &port_dev->child->dev);
>
> When a Thunderbolt dock is unplugged, two teardown paths race:
>
> 1. The component framework calls connector_unbind() first, which sets
>    port_dev->connector = NULL without calling typec_deattach().  This
>    leaves port->usb2_dev/port->usb3_dev in struct typec_port pointing at
>    the USB device that is about to be freed.
>
> 2. usb_disconnect() then calls typec_deattach(port_dev->connector, ...),
>    but port_dev->connector is already NULL, so the call is a no-op and
>    port->usb2_dev is never cleared.
>
> 3. Concurrently, UCSI detects a PD partner-disconnect event and calls
>    typec_unregister_partner(), which reads port->usb2_dev (now a dangling
>    pointer to freed memory) and passes it to typec_partner_unlink_device()
>    -> sysfs_remove_link() -> dev_name() on the freed device, corrupting
>    the typec/UCSI partner state.
>
> This corruption leaves the Thunderbolt tunnel in an inconsistent state on
> the next dock hot-plug.  On affected hardware the dock's I225/igc NIC fails
> to enumerate: AER fires a slot reset while the igc driver is still
> initialising ("PCIe link lost"), and the subsequent igc_reset attempt hits
> igc_rd32 on an already-detached device:
>
>     igc 0000:2e:00.0 eth0: PCIe link lost, device now detached
>     igc: Failed to read reg 0x0!
>     WARNING: CPU: 9 PID: 129 at drivers/net/ethernet/intel/igc/igc_main.c:7005
>              igc_rd32+0xa4/0xc0 [igc]
>     Call Trace:
>      igc_disable_pcie_master+0x16/0xa0 [igc]
>      igc_reset_hw_base+0x14/0x170 [igc]
>      igc_reset+0x63/0x110 [igc]
>      igc_io_slot_reset+0x9e/0xd0 [igc]
>      report_slot_reset+0x5d/0xc0
>      pcie_do_recovery+0x209/0x400
>      aer_isr_one_error_type+0x235/0x430
>      aer_isr+0x4e/0x80
>      irq_thread+0xf4/0x1f0
>
> 4. UCSI later handles the PD partner-disconnect and calls
>    typec_unregister_partner(), which still sees the stale port->usb2_dev
>    and tries to remove its sysfs link a second time:
>
>    kernfs: can not remove 'typec', no directory
>    WARNING: CPU: 6 PID: 55 at fs/kernfs/dir.c:1706 kernfs_remove_by_name_ns+0xe9/0xf0
>    Workqueue: events ucsi_handle_connector_change [typec_ucsi]
>    Call Trace:
>     sysfs_remove_link+0x19/0x50
>     typec_unregister_partner+0x6e/0x120 [typec]
>     ucsi_unregister_partner+0x107/0x150 [typec_ucsi]
>     ucsi_handle_connector_change+0x3ec/0x490 [typec_ucsi]
>     process_one_work+0x18e/0x3e0
>     worker_thread+0x2e3/0x420
>     kthread+0x10a/0x230
>     ret_from_fork+0x121/0x140
>     ret_from_fork_asm+0x1a/0x30
>
>    With worse timing the same stale pointer is dereferenced after the
>    backing memory is freed, turning the warning into a use-after-free.
>
> Fix the asymmetry: call typec_deattach() before clearing
> port_dev->connector, matching what connector_bind() does on the bind side.
> typec_partner_deattach() is already protected by port->partner_link_lock,
> so it serialises safely with the concurrent typec_unregister_partner() path.
>
> Fixes: 11110783f5ea ("usb: Inform the USB Type-C class about enumerated devices")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Chia-Lin Kao (AceLan) <acelan.kao@xxxxxxxxxxxxx>
> ---
>  drivers/usb/core/port.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
> index b1364f0c384ce..b4452b665f591 100644
> --- a/drivers/usb/core/port.c
> +++ b/drivers/usb/core/port.c
> @@ -740,6 +740,8 @@ static void connector_unbind(struct device *dev, struct device *connector, void
>
>         sysfs_remove_link(&connector->kobj, dev_name(dev));
>         sysfs_remove_link(&dev->kobj, "connector");
> +       if (port_dev->child)
> +               typec_deattach(port_dev->connector, &port_dev->child->dev);
>         port_dev->connector = NULL;
>  }
>
> --
> 2.53.0
>

Hi,

Just a gentle ping, please help to review this path.
Thanks.