In the Linux kernel, the following vulnerability has been resolved:
usb: core: port: Deattach Type-C connector on component unbind
connector_unbind() is the mirror of connector_bind(), but it is missing
the symmetric call to typec_deattach() that connector_bind() makes via:
<pre>
if (port_dev->child)
typec_attach(port_dev->connector, &port_dev->child->dev);
</pre>
When a Thunderbolt dock is unplugged, two teardown paths race:
-
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.
-
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.
-
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:
<pre>
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
</pre>
- 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.