In the Linux kernel, the following vulnerability has been resolved:
usb: typec: ucsi: Fix race condition and ordering in port unregistration
A synchronization issue exists during port unregistration where pending
partner work items can race against workqueue destruction, leading to
use-after-free conditions:
cros_ec_ucsi cros_ec_ucsi.3.auto: error -ETIMEDOUT: PPM init failed
BUG: kernel NULL pointer dereference, address: 0000000000000000
RIP: 0010:__queue_work+0x83/0x4a0
Call Trace:
<IRQ>
__cfi_delayed_work_timer_fn+0x10/0x10
run_timer_softirq+0x3b6/0xbd0
sched_clock_cpu+0xc/0x110
irq_exit_rcu+0x18d/0x330
fred_sysvec_apic_timer_interrupt+0x5e/0x80
Fix this by ensuring strict ordering and proper serialization during
teardown:
- Move ucsi_unregister_partner() to the beginning of the teardown
sequence and protect it under the connector mutex lock.
- Ensure all pending partner tasks are explicitly flushed and finished
before the workqueue is destroyed.
- Switch from mod_delayed_work() to a cancel_delayed_work() and
queue_delayed_work() sequence. This guarantees that items currently marked
as pending won't be scheduled an additional time, preventing a double
release of resources which leads to the following crash:
Oops: general protection fault, probably for non-canonical address
0xdead000000000122: 0000 [#1] SMP NOPTI
Workqueue: cros_ec_ucsi.3.auto-con2 ucsi_poll_worker
RIP: 0010:ucsi_poll_worker+0x65/0x1e0
Call Trace:
<TASK>
process_scheduled_works+0x218/0x6d0
worker_thread+0x188/0x3f0
__cfi_worker_thread+0x10/0x10
kthread+0x226/0x2a0
To ensure these rules are applied identically across both the normal
teardown and the ucsi_init() error paths, consolidate the cleanup logic
into a new helper, ucsi_unregister_port().