Re: REGRESSION: [PATCH] usb: typec: ucsi: Fix race condition and ordering in port unregistration
From: Borah, Chaitanya Kumar
Date: Thu Jul 16 2026 - 09:36:09 EST
On 7/16/2026 2:45 PM, Andrei Kuchynski wrote:
On Thu, Jul 16, 2026 at 10:28 AM Borah, Chaitanya Kumar
<chaitanya.kumar.borah@xxxxxxxxx> wrote:
Hello Andrei,
On 7/7/2026 7:47 PM, Andrei Kuchynski wrote:
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:
1. Move ucsi_unregister_partner() to the beginning of the teardown
sequence and protect it under the connector mutex lock.
2. Ensure all pending partner tasks are explicitly flushed and finished
before the workqueue is destroyed.
3. 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().
This seems to be causing regression in our linux-next CI. [1]
<6>[ 18.008557] ------------[ cut here ]------------
<4>[ 18.013166] DEBUG_LOCKS_WARN_ON(1)
<4>[ 18.013167] WARNING: kernel/locking/lockdep.c:238 at
__lock_acquire+0xa59/0x2750, CPU#1: kworker/u89:1/172
...
<4>[ 18.159950] Hardware name: Intel Corporation Meteor Lake Client
Platform/MTL-P DDR5 SODIMM SBS RVP, BIOS
MTLPFWI1.R00.3471.D89.2401091901 01/09/2024
<4>[ 18.173125] Workqueue: events_dfl_long ucsi_init_work [typec_ucsi]
<4>[ 18.179257] RIP: 0010:__lock_acquire+0xa60/0x2750
<4>[ 18.183927] Code: 44 8b 5d a8 85 c0 0f 84 98 fd ff ff 44 8b 35 07
0b 72 02 45 85 f6 0f 85 88 fd ff ff 48 8d 3d 27 25 73 02 48 c7 c6 1b 51
27 83 <67> 48 0f b9 3a 31 c0 44 8b 5d a8 44 8b 4d b0 e9 c6 f7 ff ff 31 d2
...
<4>[ 18.263886] PKRU: 55555554
<4>[ 18.266583] Call Trace:
<4>[ 18.269014] <TASK>
<4>[ 18.271110] ? mark_held_locks+0x46/0x90
<4>[ 18.275007] lock_acquire+0xd9/0x2e0
<4>[ 18.278562] ? ucsi_unregister_port+0x36/0x140 [typec_ucsi]
<4>[ 18.284096] __mutex_lock+0xb2/0x1020
<4>[ 18.287735] ? ucsi_unregister_port+0x36/0x140 [typec_ucsi]
<4>[ 18.293265] ? ucsi_unregister_port+0x36/0x140 [typec_ucsi]
<4>[ 18.298797] ? synchronize_rcu_expedited+0x2b2/0x300
<4>[ 18.303724] ? __pfx_autoremove_wake_function+0x10/0x10
<4>[ 18.308912] mutex_lock_nested+0x1b/0x30
<4>[ 18.312806] ? mutex_lock_nested+0x1b/0x30
<4>[ 18.316878] ucsi_unregister_port+0x36/0x140 [typec_ucsi]
<4>[ 18.322238] ucsi_init_work+0x66d/0xc10 [typec_ucsi]
<4>[ 18.327167] process_one_work+0x2ad/0x8b0
<4>[ 18.331158] worker_thread+0x200/0x3f0
<4>[ 18.334886] ? __pfx_worker_thread+0x10/0x10
<4>[ 18.339128] kthread+0x10d/0x150
<4>[ 18.342339] ? __pfx_kthread+0x10/0x10
<4>[ 18.346067] ret_from_fork+0x3bd/0x470
<4>[ 18.349795] ? __pfx_kthread+0x10/0x10
<4>[ 18.353522] ret_from_fork_asm+0x1a/0x30
<4>[ 18.357420] </TASK>
Detailed log can be seen found in [2]
We confirmed that reverting the patch solves the issue.
Could you please check why the patch causes this regression and provide
a fix if necessary?
Regards
Chaitanya
[1] https://intel-gfx-ci.01.org/tree/linux-next/combined-alt.html?
[2]
https://intel-gfx-ci.01.org/tree/linux-next/next-20260714/bat-mtlp-9/boot0.txt
-- Bisect Logs --
git bisect start
# status: waiting for both good and bad commits
# good: [5f1b513690edf51727e6928b97705b6437f9a98e] Merge remote-tracking
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# status: waiting for bad commit, 1 good commit known
# bad: [49362394dad7df66c274c867a271394c10ca2bb8] Add linux-next
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git bisect good 15eab2dd63a97587405ab6bfaad9728d5b35b5fe
# bad: [c2e819be6a5c7f34344926b4bd7e3dfca58cf48a] usb: gadget: printer:
fix infinite loop in printer_read()
git bisect bad c2e819be6a5c7f34344926b4bd7e3dfca58cf48a
# good: [29a142d3e8b35ebc9e0bcc78f4bc26c9b6a9ac0b] USB: gadget:
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# good: [1febec7e47cdcd01f43fb0211094e3010474666e] usb: gadget: f_ncm:
validate datagram bounds in ncm_unwrap_ntb()
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git bisect bad 0583f2fbf8f86ae3a0ce054f96783dd83e65d9bb
# bad: [7aa7d4bf9d3fa9a6a47b640ad103ab433b7ff261] usb: typec: ucsi: Fix
race condition and ordering in port unregistration
git bisect bad 7aa7d4bf9d3fa9a6a47b640ad103ab433b7ff261
# first bad commit: [7aa7d4bf9d3fa9a6a47b640ad103ab433b7ff261] usb:
typec: ucsi: Fix race condition and ordering in port unregistration
Cc: stable@xxxxxxxxxxxxxxx
Fixes: b9aa02ca39a4 ("usb: typec: ucsi: Add polling mechanism for partner tasks like alt mode checking")
Fixes: b13abcb7ddd8 ("usb: typec: ucsi: Fix NULL pointer access")
Fixes: fac4b8633fd6 ("usb: ucsi: Ensure connector delayed work items are flushed")
Signed-off-by: Andrei Kuchynski <akuchynski@xxxxxxxxxxxx>
---
drivers/usb/typec/ucsi/ucsi.c | 82 +++++++++++++++++------------------
1 file changed, 39 insertions(+), 43 deletions(-)
diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
index 92166a3725b16..d9668ed7c80ea 100644
--- a/drivers/usb/typec/ucsi/ucsi.c
+++ b/drivers/usb/typec/ucsi/ucsi.c
@@ -1845,6 +1845,42 @@ static int ucsi_register_port(struct ucsi *ucsi, struct ucsi_connector *con)
return ret;
}
+static void ucsi_unregister_port(struct ucsi_connector *con)
+{
+ struct ucsi_work *uwork;
+
+ if (con->wq) {
+ mutex_lock(&con->lock);
+ ucsi_unregister_partner(con);
+ /*
+ * queue delayed items immediately so they can execute
+ * and free themselves before the wq is destroyed
+ */
+ list_for_each_entry(uwork, &con->partner_tasks, node) {
+ if (cancel_delayed_work(&uwork->work))
+ queue_delayed_work(con->wq, &uwork->work, 0);
+ }
+ mutex_unlock(&con->lock);
+
+ destroy_workqueue(con->wq);
+ con->wq = NULL;
+ } else {
+ ucsi_unregister_partner(con);
+ }
+
+ ucsi_unregister_altmodes(con, UCSI_RECIPIENT_CON);
+ ucsi_unregister_port_psy(con);
+
+ usb_power_delivery_unregister_capabilities(con->port_sink_caps);
+ con->port_sink_caps = NULL;
+ usb_power_delivery_unregister_capabilities(con->port_source_caps);
+ con->port_source_caps = NULL;
+ usb_power_delivery_unregister(con->pd);
+ con->pd = NULL;
+ typec_unregister_port(con->port);
+ con->port = NULL;
+}
+
static u64 ucsi_get_supported_notifications(struct ucsi *ucsi)
{
u16 features = ucsi->cap.features;
@@ -1971,22 +2007,8 @@ static int ucsi_init(struct ucsi *ucsi)
for (i = 0; i < ucsi->cap.num_connectors; i++)
lockdep_unregister_key(&connector[i].lock_key);
- for (con = connector; con->port; con++) {
- if (con->wq)
- destroy_workqueue(con->wq);
- ucsi_unregister_partner(con);
- ucsi_unregister_altmodes(con, UCSI_RECIPIENT_CON);
- ucsi_unregister_port_psy(con);
-
- usb_power_delivery_unregister_capabilities(con->port_sink_caps);
- con->port_sink_caps = NULL;
- usb_power_delivery_unregister_capabilities(con->port_source_caps);
- con->port_source_caps = NULL;
- usb_power_delivery_unregister(con->pd);
- con->pd = NULL;
- typec_unregister_port(con->port);
- con->port = NULL;
- }
+ for (con = connector; con->port; con++)
+ ucsi_unregister_port(con);
Hi Chaitanya,
Thank you for spotting this!
Could you verify if calling lockdep_unregister_key(&connector[i].lock_key)
after ucsi_unregister_port(con) resolves the issue?
for (con = connector; con->port; con++)
ucsi_unregister_port(con);
for (i = 0; i < ucsi->cap.num_connectors; i++)
lockdep_unregister_key(&connector[i].lock_key);
I will also try testing this on my side.
Thank you Andrei for the patch. It seems to work for us.
==
Chaitanya
Thanks,
Andrei