Re: REGRESSION: [PATCH] usb: typec: ucsi: Fix race condition and ordering in port unregistration
From: Andrei Kuchynski
Date: Thu Jul 16 2026 - 09:41:49 EST
On Thu, Jul 16, 2026 at 3:23 PM Borah, Chaitanya Kumar
<chaitanya.kumar.borah@xxxxxxxxx> wrote:
>
>
>
> 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
> >> branch 'spi/for-7.3' into spi-next
> >> git bisect good 5f1b513690edf51727e6928b97705b6437f9a98e
> >> # status: waiting for bad commit, 1 good commit known
> >> # bad: [49362394dad7df66c274c867a271394c10ca2bb8] Add linux-next
> >> specific files for 20260713
> >> git bisect bad 49362394dad7df66c274c867a271394c10ca2bb8
> >> # bad: [dffddeb046466ed57038295bde28b42b7506a12b] Merge branch
> >> 'nand/next' of https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git
> >> git bisect bad dffddeb046466ed57038295bde28b42b7506a12b
> >> # bad: [d154d0766bf3fe830e1bf98fb2d8648294a4a8da] Merge branch
> >> 'for-next' of
> >> https://git.kernel.org/pub/scm/linux/kernel/git/khilman/linux-omap.git
> >> git bisect bad d154d0766bf3fe830e1bf98fb2d8648294a4a8da
> >> # bad: [671b0fd929bec9ebf863cb376baf9b9d1226a510] Merge branch 'master'
> >> of https://git.kernel.org/pub/scm/linux/kernel/git/kvms390/linux.git
> >> git bisect bad 671b0fd929bec9ebf863cb376baf9b9d1226a510
> >> # good: [f4fb100039e96211609dfc44fb24b9e4a8a0f2f9] Merge tag
> >> 's390-7.2-4' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux
> >> git bisect good f4fb100039e96211609dfc44fb24b9e4a8a0f2f9
> >> # good: [c296d513e034df93ddb230ad1c7a118d6b58750c] Merge branch
> >> 'arm/fixes' of https://git.kernel.org/pub/scm/linux/kernel/git/soc/soc.git
> >> git bisect good c296d513e034df93ddb230ad1c7a118d6b58750c
> >> # good: [de53c0a584f08f31eb957f8c849a59fb33b27fa8] Merge branch 'for-rc'
> >> of https://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma.git
> >> git bisect good de53c0a584f08f31eb957f8c849a59fb33b27fa8
> >> # bad: [a6969de5a038bc08a948ada52bd7199a8dfa6cec] Merge branch
> >> 'usb-linus' of
> >> https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
> >> git bisect bad a6969de5a038bc08a948ada52bd7199a8dfa6cec
> >> # good: [15eab2dd63a97587405ab6bfaad9728d5b35b5fe] Merge tag
> >> 'asoc-fix-v7.2-rc2' of
> >> https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound into for-linus
> >> git bisect good 15eab2dd63a97587405ab6bfaad9728d5b35b5fe
> >> # bad: [c2e819be6a5c7f34344926b4bd7e3dfca58cf48a] usb: gadget: printer:
> >> fix infinite loop in printer_read()
> >> git bisect bad c2e819be6a5c7f34344926b4bd7e3dfca58cf48a
> >> # good: [29a142d3e8b35ebc9e0bcc78f4bc26c9b6a9ac0b] USB: gadget:
> >> snps-udc: fix device name leak on probe failure
> >> git bisect good 29a142d3e8b35ebc9e0bcc78f4bc26c9b6a9ac0b
> >> # good: [1febec7e47cdcd01f43fb0211094e3010474666e] usb: gadget: f_ncm:
> >> validate datagram bounds in ncm_unwrap_ntb()
> >> git bisect good 1febec7e47cdcd01f43fb0211094e3010474666e
> >> # bad: [0583f2fbf8f86ae3a0ce054f96783dd83e65d9bb] usb: gadget: udc: bdc:
> >> free IRQ and drain func_wake_notify before teardown
> >> 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.
>
Hi Chaitanya,
Thanks for the testing!
I will prepare a fix or maybe V2 of this patch.
Could you please share your configuration details? Specifically, do you
have any of the following enabled?
CONFIG_DEBUG_LOCKDEP
CONFIG_LOCK_STAT
CONFIG_LOCKDEP_SMALL
CONFIG_DEBUG_LOCKDEP
CONFIG_PROVE_LOCKING
I am still not able to reproduce it.
Thanks,
Andrei