[PATCH 0/4] usb: stop timers/works left armed on teardown

[PATCH 0/4] usb: stop timers/works left armed on teardown

[Chengyu Liu]

The teardown paths in these four drivers do not quiesce every producer
of asynchronous work before draining it: an interrupt handler may still
queue or re-arm a timer or work item after the cancellation, while the
corresponding object is being torn down.  In three of them the IRQ is
devm-managed and freed only at detach, after remove() returns; in musb
the plain free_irq() happens later in the same remove path.  Either way
a late interrupt re-arms the callback, which then runs on freed memory:

  [1/4] musb core: musb_stage0_irq() can schedule irq_work while
        handling stage-0 USB interrupts, and the work can also re-arm
        itself from the session recheck path; musb_remove() cancels it
        before masking the interrupts and before free_irq().
  [2/4] musb dsps glue: the devm VBUS interrupt outlives the child
        teardown that deletes musb->dev_timer; its handler re-arms
        the timer via dsps_mod_timer().
  [3/4] r8a66597: r8a66597_remove() deletes the timer while the devm
        IRQ can still re-arm it from the VBINT path.
  [4/4] gpio-vbus: gpio_vbus_remove() cancels the work while the devm
        GPIO interrupt can still re-arm it (100 ms debounce delay).

Two further instances of this defect class found in the same sweep -
pch_udc and lpc32xx_udc - are being handled in Hyunjung Ko's
"usb: gadget: pch_udc: drain vbus GPIO works before freeing the
device" and "usb: gadget: lpc32xx_udc: drain the pullup work on
removal" threads, so they are not part of this series.

Testing:
  [1-3/4] build-tested on x86_64 (COMPILE_TEST where needed); they
        require hardware we do not have, so no runtime reproducer.
  [4/4] additionally confirmed with a KASAN reproducer: the driver
        probed on a gpio-sim chip in QEMU, slab-use-after-free write
        in __run_timer_base() after unregister (5/5 runs), clean with
        the fix (0/5).  The KASAN report and the reproducer kit follow
        in this thread.

All found by static analysis.  Fixes written with AI assistance.

Chengyu Liu (4):
  usb: musb: cancel irq_work after masking interrupts in musb_remove()
  usb: musb: dsps: free the VBUS interrupt before the child teardown
  usb: gadget: r8a66597: free the IRQ before deleting the timer
  usb: phy: gpio-vbus: free the interrupt before cancelling the work

 drivers/usb/gadget/udc/r8a66597-udc.c  |  8 ++++++++
 drivers/usb/gadget/udc/r8a66597-udc.h  |  1 +
 drivers/usb/musb/musb_core.c           | 10 +++++++++-
 drivers/usb/musb/musb_dsps.c           | 11 +++++++++++
 drivers/usb/phy/phy-gpio-vbus-usb.c    |  8 ++++++++
 5 files changed, 37 insertions(+), 1 deletion(-)


Signed-off-by: Chengyu Liu <lui2012qwq@gmail.com>
-- 
2.25.1

[PATCH 1/4] usb: musb: cancel irq_work after masking interrupts in musb_remove()

[Chengyu Liu]

musb_stage0_irq() can schedule irq_work while handling stage-0 USB
interrupts, and the work can also re-arm itself from the session
recheck path (musb_pm_runtime_check_session()).  musb_remove()
cancels irq_work while the interrupt is still enabled and the IRQ
line not yet freed: an interrupt landing after the cancel re-arms
the work, and musb_irq_work() then runs after musb_free() has
released the struct.

Move the cancel behind musb_disable_interrupts() and synchronize the
IRQ line first, so no handler can be running or re-arm the work past
the cancel.

Found by static analysis.

Fixes: c5340bd14336 ("usb: musb: cancel work on removal")
Cc: stable@vger.kernel.org
Signed-off-by: Chengyu Liu <lui2012qwq@gmail.com>
---
Build-tested on x86_64: musb_core.o compiles clean
(USB_MUSB_HDRC).  No runtime reproducer: requires MUSB-based OTG
hardware.  Fix written with AI assistance.

 drivers/usb/musb/musb_core.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/musb/musb_core.c b/drivers/usb/musb/musb_core.c
index 9b63b56edc45..eea43a20a1d0 100644
--- a/drivers/usb/musb/musb_core.c
+++ b/drivers/usb/musb/musb_core.c
@@ -2630,7 +2630,6 @@ static void musb_remove(struct platform_device *pdev)
 	 */
 	musb_exit_debugfs(musb);
 
-	cancel_delayed_work_sync(&musb->irq_work);
 	cancel_delayed_work_sync(&musb->finish_resume_work);
 	cancel_delayed_work_sync(&musb->deassert_reset_work);
 	pm_runtime_get_sync(musb->controller);
@@ -2642,6 +2641,15 @@ static void musb_remove(struct platform_device *pdev)
 	musb_disable_interrupts(musb);
 	musb_writeb(musb->mregs, MUSB_DEVCTL, 0);
 	spin_unlock_irqrestore(&musb->lock, flags);
+
+	/*
+	 * musb_stage0_irq() arms irq_work, so it can only be cancelled
+	 * for good once interrupts are masked and any in-flight handler
+	 * has completed.
+	 */
+	synchronize_irq(musb->nIrq);
+	cancel_delayed_work_sync(&musb->irq_work);
+
 	musb_platform_exit(musb);
 
 	pm_runtime_dont_use_autosuspend(musb->controller);
-- 
2.25.1

Re: [PATCH 1/4] usb: musb: cancel irq_work after masking interrupts in musb_remove()

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Low] usb: musb: inaccurate Fixes trailer in commit message for
  musb_remove()
--

commit e08f859cc70a9eed1b7e88c3628f7b1178dcabc5
Author: Chengyu Liu <lui2012qwq@gmail.com>

> usb: musb: cancel irq_work after masking interrupts in musb_remove()
>
> musb_stage0_irq() can schedule irq_work while handling stage-0 USB
> interrupts, and the work can also re-arm itself from the session
> recheck path (musb_pm_runtime_check_session()).  musb_remove()
> cancels irq_work while the interrupt is still enabled and the IRQ
> line not yet freed: an interrupt landing after the cancel re-arms
> the work, and musb_irq_work() then runs after musb_free() has
> released the struct.
>
> Move the cancel behind musb_disable_interrupts() and synchronize the
> IRQ line first, so no handler can be running or re-arm the work past
> the cancel.
>
> Found by static analysis.
>
> Fixes: c5340bd14336 ("usb: musb: cancel work on removal")
> Cc: stable@vger.kernel.org
> Signed-off-by: Chengyu Liu <lui2012qwq@gmail.com>

[Severity: Low]
In c5340bd14336 ("usb: musb: cancel work on removal"), cancel_work_sync()
was placed in musb_free() immediately after free_irq() and after
musb_shutdown() had disabled interrupts.  66fadea5b79c ("usb: musb: only
cancel work if it is initialized") later moved the cancel into
musb_remove() ahead of free_irq(), and f730f205cc51 ("usb: musb: Split PM
runtime between wrapper IP and musb core") moved it ahead of
musb_disable_interrupts().

Should the Fixes: tag reference f730f205cc51 ("usb: musb: Split PM runtime
between wrapper IP and musb core") instead?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261112160448.41566-1-lui2012qwq@gmail.com?part=1

Re: [PATCH 1/4] usb: musb: cancel irq_work after masking interrupts in musb_remove()

[Chengyu Liu]

Thanks, f730f205cc51 is the right one. I'll carry the corrected Fixes
tag if the series needs a respin.

[PATCH 2/4] usb: musb: dsps: free the VBUS interrupt before the child teardown

[Chengyu Liu]

dsps_remove() unregisters the musb child, which deletes
musb->dev_timer and frees the structure, while the glue's VBUS
interrupt is devm-managed and only freed after dsps_remove() returns.
dsps_vbus_threaded_irq() re-arms the timer via dsps_mod_timer(), so
a VBUS event in between re-arms dev_timer past its deletion and
otg_timer() runs on freed memory.

Free the VBUS interrupt first, which also waits for any in-flight
handler, so nothing can re-arm the timer once the child teardown
runs.

Found by static analysis.

Fixes: 369469a92393 ("usb: musb: Add support for optional VBUS irq to dsps glue layer")
Cc: stable@vger.kernel.org
Signed-off-by: Chengyu Liu <lui2012qwq@gmail.com>
---
Build-tested on x86_64: musb_dsps.o compiles clean
(USB_MUSB_DSPS).  No runtime reproducer: requires AM33xx/DSPS
hardware.  Fix written with AI assistance.

 drivers/usb/musb/musb_dsps.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/usb/musb/musb_dsps.c b/drivers/usb/musb/musb_dsps.c
index 91d8712efa41..69c8b4b3ffa7 100644
--- a/drivers/usb/musb/musb_dsps.c
+++ b/drivers/usb/musb/musb_dsps.c
@@ -942,6 +942,17 @@ static void dsps_remove(struct platform_device *pdev)
 {
 	struct dsps_glue *glue = platform_get_drvdata(pdev);
 
+	/*
+	 * The VBUS interrupt handler re-arms musb->dev_timer via
+	 * dsps_mod_timer(); the IRQ is devm-managed and would only be
+	 * freed after this function returns, while the child teardown
+	 * below deletes the timer and frees the musb structure.  Free
+	 * the interrupt first so no VBUS event can re-arm the timer
+	 * past that point.
+	 */
+	if (glue->vbus_irq)
+		devm_free_irq(glue->dev, glue->vbus_irq, glue);
+
 	platform_device_unregister(glue->musb);
 
 	pm_runtime_disable(&pdev->dev);
-- 
2.25.1

[PATCH 3/4] usb: gadget: r8a66597: free the IRQ before deleting the timer

[Chengyu Liu]

r8a66597_remove() deletes r8a66597->timer while the interrupt is
still live: the IRQ is devm-managed and only freed at detach, and
r8a66597_irq() re-arms the timer when sampling VBUS (VBINT).  An
interrupt landing after timer_delete_sync() re-arms the timer, and
r8a66597_timer() then runs on freed memory.

Store the requested IRQ number at probe time and free it before
deleting the timer; freeing also waits for any running handler, so
nothing can re-arm the timer past the delete.

Found by static analysis.

Fixes: c41442474a26 ("usb: gadget: R8A66597 peripheral controller support.")
Cc: stable@vger.kernel.org
Signed-off-by: Chengyu Liu <lui2012qwq@gmail.com>
---
Build-tested on x86_64: r8a66597-udc.o compiles clean
(USB_R8A66597 + COMPILE_TEST).  No runtime reproducer: requires
R8A66597 hardware.  Fix written with AI assistance.

 drivers/usb/gadget/udc/r8a66597-udc.c | 8 ++++++++
 drivers/usb/gadget/udc/r8a66597-udc.h | 1 +
 2 files changed, 9 insertions(+)

diff --git a/drivers/usb/gadget/udc/r8a66597-udc.c b/drivers/usb/gadget/udc/r8a66597-udc.c
index 469075b064ba..bfccc6565e0a 100644
--- a/drivers/usb/gadget/udc/r8a66597-udc.c
+++ b/drivers/usb/gadget/udc/r8a66597-udc.c
@@ -1810,6 +1810,13 @@ static void r8a66597_remove(struct platform_device *pdev)
 	struct r8a66597		*r8a66597 = platform_get_drvdata(pdev);
 
 	usb_del_gadget_udc(&r8a66597->gadget);
+
+	/*
+	 * The interrupt handler re-arms the timer on VBUS changes; the
+	 * IRQ is devm-managed and freed only at detach, so free it
+	 * before deleting the timer.
+	 */
+	devm_free_irq(&pdev->dev, r8a66597->irq, r8a66597);
 	timer_delete_sync(&r8a66597->timer);
 	r8a66597_free_request(&r8a66597->ep[0].ep, r8a66597->ep0_req);
 
@@ -1896,6 +1903,7 @@ static int r8a66597_probe(struct platform_device *pdev)
 			       udc_name, r8a66597);
 	if (ret < 0)
 		goto clean_up2;
+	r8a66597->irq = irq;
 
 	INIT_LIST_HEAD(&r8a66597->gadget.ep_list);
 	r8a66597->gadget.ep0 = &r8a66597->ep[0].ep;
diff --git a/drivers/usb/gadget/udc/r8a66597-udc.h b/drivers/usb/gadget/udc/r8a66597-udc.h
index 9a115caba661..08acabe02421 100644
--- a/drivers/usb/gadget/udc/r8a66597-udc.h
+++ b/drivers/usb/gadget/udc/r8a66597-udc.h
@@ -110,6 +110,7 @@ struct r8a66597 {
 	unsigned char interrupt;
 	unsigned char isochronous;
 	unsigned char num_dma;
+	int irq;
 
 	unsigned irq_sense_low:1;
 };
-- 
2.25.1

Re: [PATCH 3/4] usb: gadget: r8a66597: free the IRQ before deleting the timer

[sashiko-bot]

> r8a66597_remove() deletes r8a66597->timer while the interrupt is
> still live: the IRQ is devm-managed and only freed at detach, and
> r8a66597_irq() re-arms the timer when sampling VBUS (VBINT).  An
> interrupt landing after timer_delete_sync() re-arms the timer, and
> r8a66597_timer() then runs on freed memory.
> 
> Store the requested IRQ number at probe time and free it before
> deleting the timer; freeing also waits for any running handler, so
> nothing can re-arm the timer past the delete.
> 
> Found by static analysis.
> 
> Fixes: c41442474a26 ("usb: gadget: R8A66597 peripheral controller support.")
> Cc: stable@vger.kernel.org
> Signed-off-by: Chengyu Liu <lui2012qwq@gmail.com>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261112160448.41566-1-lui2012qwq@gmail.com?part=3

[PATCH 4/4] usb: phy: gpio-vbus: free the interrupt before cancelling the work

[Chengyu Liu]

gpio_vbus_remove() cancels gpio_vbus->work while the VBUS sensing GPIO
interrupt is still live: it is devm-managed and freed only at detach,
and gpio_vbus_irq() schedules the work with a 100 ms debounce delay.
A plug event landing after the cancel re-arms the work, and its timer
then fires on the freed gpio_vbus_data.

Free the interrupt first, which also waits for any running handler,
so nothing can re-arm the work past the cancel.

Found by static analysis and confirmed with a KASAN reproducer:
slab-use-after-free write in __run_timer_base() within one debounce
interval of unregistering the device while its VBUS GPIO is toggled
(object allocated by gpio_vbus_probe() via devm_kmalloc(), freed by
devres_release_all() at unbind).

Fixes: c2344f13b59e ("USB: gpio_vbus: add delayed vbus_session calls")
Cc: stable@vger.kernel.org
Signed-off-by: Chengyu Liu <lui2012qwq@gmail.com>
---
The reproducer instantiates the unmodified driver on a gpio-sim
chip in QEMU and toggles the line while the device is unregistered;
it widens the remove()-to-detach window with a 500 ms sleep, logic
otherwise unmodified.  Repeated runs: 5/5 KASAN splats without the
fix, 0/5 with it.  The KASAN report and the reproducer kit follow
in this thread.  Also build-tested on x86_64 (USB_GPIO_VBUS).
Fix written with AI assistance.

 drivers/usb/phy/phy-gpio-vbus-usb.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/usb/phy/phy-gpio-vbus-usb.c b/drivers/usb/phy/phy-gpio-vbus-usb.c
index 60b7c1219dd2..82d2301c3804 100644
--- a/drivers/usb/phy/phy-gpio-vbus-usb.c
+++ b/drivers/usb/phy/phy-gpio-vbus-usb.c
@@ -325,6 +325,14 @@ static void gpio_vbus_remove(struct platform_device *pdev)
 	struct gpio_vbus_data *gpio_vbus = platform_get_drvdata(pdev);
 
 	device_init_wakeup(&pdev->dev, 0);
+
+	/*
+	 * The VBUS sensing GPIO interrupt is devm-managed and freed only
+	 * at detach, and its handler schedules the work with a 100ms
+	 * delay; free the interrupt before cancelling the work so a
+	 * late plug event cannot re-arm it past the cancel.
+	 */
+	devm_free_irq(&pdev->dev, gpio_vbus->irq, pdev);
 	cancel_delayed_work_sync(&gpio_vbus->work);
 
 	usb_remove_phy(&gpio_vbus->phy);
-- 
2.25.1

Re: [PATCH 4/4] usb: phy: gpio-vbus: free the interrupt before cancelling the work

[sashiko-bot]

> gpio_vbus_remove() cancels gpio_vbus->work while the VBUS sensing GPIO
> interrupt is still live: it is devm-managed and freed only at detach,
> and gpio_vbus_irq() schedules the work with a 100 ms debounce delay.
> A plug event landing after the cancel re-arms the work, and its timer
> then fires on the freed gpio_vbus_data.
> 
> Free the interrupt first, which also waits for any running handler,
> so nothing can re-arm the work past the cancel.
> 
> Found by static analysis and confirmed with a KASAN reproducer:
> slab-use-after-free write in __run_timer_base() within one debounce
> interval of unregistering the device while its VBUS GPIO is toggled
> (object allocated by gpio_vbus_probe() via devm_kmalloc(), freed by
> devres_release_all() at unbind).
> 
> Fixes: c2344f13b59e ("USB: gpio_vbus: add delayed vbus_session calls")
> Cc: stable@vger.kernel.org
> Signed-off-by: Chengyu Liu <lui2012qwq@gmail.com>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261112160448.41566-1-lui2012qwq@gmail.com?part=4

Re: [PATCH 0/4] usb: stop timers/works left armed on teardown

[Chengyu Liu]

The KASAN report and the reproducer kit for the gpio-vbus instance
[4/4], as promised in the cover letter.

Environment: QEMU x86_64, generic KASAN kernel (v7.3-rc7 plus unrelated
local commits; config: KASAN/KASAN_GENERIC=y, GPIOLIB=y, GPIO_SIM=y,
CONFIGFS_FS=y, USB_GADGET=m, USB_GPIO_VBUS=m),
phy-gpio-vbus-usb built as a module.  The driver under test is
unmodified except for the disclosed 500 ms sleep widening the
remove()-to-detach window.

Setup: a one-line gpio-sim chip labelled "vbus-sim" stands in for the
VBUS sense GPIO; writing its "pull" sysfs attribute generates real GPIO
edge interrupts.  The vbus_rig module registers a gpiod lookup table and
the "gpio-vbus" platform device, so the real driver probes it, and
attaches a dummy usb_gadget to phy->otg->gadget so gpio_vbus_irq() takes
its normal schedule_delayed_work() path (a UDC provides this on real
hardware); the module fails to load if the phy cannot be attached, so a
clean run cannot be a setup artifact.  rmmod vbus_rig runs the real
gpio_vbus_remove() while the line is being toggled.

Results over repeated runs of the same script:

    vulnerable kernel: 5/5 runs, KASAN slab-use-after-free each time
    patched kernel:    5/5 runs, clean

Representative vulnerable splat (VBUS edges toggle at max rate while the
device is unregistered; an interrupt lands after the
cancel_delayed_work_sync(), re-arms the 100 ms debounce work, and the
work's timer fires after the devm release has freed gpio_vbus_data):

[    3.571772] BUG: KASAN: slab-use-after-free in __run_timer_base.part.0+0x80c/0x900
[    3.571779] Write of size 8 at addr ffff8880033291d8 by task sh/89
[    3.571781] 
[    3.571784] CPU: 0 UID: 0 PID: 89 Comm: sh Tainted: G        W  O        7.3.0-rc7-00036-gf9532d351e12-dirty #29 PREEMPT(lazy) 
[    3.571788] Tainted: [W]=WARN, [O]=OOT_MODULE
[    3.571788] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
[    3.571790] Call Trace:
[    3.571791]  <IRQ>
[    3.571792]  dump_stack_lvl+0x55/0x70
[    3.571808]  print_report+0x10d/0x5d0
[    3.571811]  ? __run_timer_base.part.0+0x80c/0x900
[    3.571813]  kasan_report+0x96/0xd0
[    3.571815]  ? __run_timer_base.part.0+0x80c/0x900
[    3.571817]  __run_timer_base.part.0+0x80c/0x900
[    3.571819]  ? __pfx___run_timer_base.part.0+0x10/0x10
[    3.571821]  ? __pfx___hrtimer_get_next_event+0x10/0x10
[    3.571825]  ? kvm_clock_read+0x15/0x30
[    3.571827]  ? __hrtimer_run_queues+0x2aa/0x580
[    3.571829]  ? clockevents_program_event+0x2b0/0x7c0
[    3.571833]  ? hrtimer_update_next_event+0x8a/0x100
[    3.571835]  run_timer_softirq+0xd6/0x190
[    3.571837]  handle_softirqs+0x184/0x5c0
[    3.571840]  ? __hrtimer_rearm_deferred+0x15d/0x460
[    3.571841]  irq_exit_rcu+0x6e/0x150
[    3.571843]  sysvec_apic_timer_interrupt+0x70/0x80
[    3.571845]  </IRQ>
[    3.571846]  <TASK>
[    3.571846]  asm_sysvec_apic_timer_interrupt+0x1a/0x20
[    3.571849] RIP: 0010:stack_depot_save_flags+0x61/0x830
[    3.571852] Code: 70 05 05 00 74 16 48 83 c4 30 44 89 e8 5b 5d 41 5c 41 5d 41 5e 41 5f c3 cc cc cc cc 89 c1 48 01 c9 89 cf 8d 04 8d 7b 71 f5 75 <83> f9 03 0f 86 36 01 00 00 89 c3 89 c1 4c 89 fe 03 5e 08 03 06 83
[    3.571854] RSP: 0018:ffff888002207a08 EFLAGS: 00000216
[    3.571856] RAX: 0000000075f571cb RBX: ffff888003880988 RCX: 0000000000000014
[    3.571858] RDX: ffffffffb3000130 RSI: 000000000000000a RDI: 0000000000000014
[    3.571859] RBP: ffff888001041640 R08: 0000000000000000 R09: ffffffffb87baec6
[    3.571859] R10: ffff888002207978 R11: ffff888002207f50 R12: 0000000000000001
[    3.571860] R13: 0000000000000000 R14: 000000000000000a R15: ffff888002207a70
[    3.571862]  ? entry_SYSCALL_64_after_hwframe+0x77/0x7f
[    3.571864]  ? stack_depot_save_flags+0x2d/0x830
[    3.571866]  ? kernfs_fop_write_iter+0x168/0x480
[    3.571868]  kasan_save_stack+0x34/0x50
[    3.571870]  ? kasan_save_stack+0x24/0x50
[    3.571871]  ? kasan_save_track+0x14/0x30
[    3.571872]  ? kasan_save_free_info+0x3a/0x60
[    3.571874]  ? __kasan_slab_free+0x43/0x70
[    3.571875]  ? kfree+0x18e/0x3c0
[    3.571877]  ? kernfs_fop_write_iter+0x168/0x480
[    3.571878]  ? vfs_write+0x87a/0xd40
[    3.571880]  ? ksys_write+0xf3/0x1c0
[    3.571881]  ? do_syscall_64+0xee/0x500
[    3.571883]  ? entry_SYSCALL_64_after_hwframe+0x77/0x7f
[    3.571885]  ? do_sys_openat2+0x308/0x450
[    3.571886]  ? kasan_save_stack+0x34/0x50
[    3.571888]  ? kasan_save_stack+0x24/0x50
[    3.571889]  ? kasan_save_track+0x14/0x30
[    3.571890]  ? kasan_save_free_info+0x3a/0x60
[    3.571892]  ? __kasan_slab_free+0x43/0x70
[    3.571893]  ? kmem_cache_free+0x1d4/0x3c0
[    3.571895]  ? do_sys_openat2+0x308/0x450
[    3.571896]  ? do_sys_open+0x8d/0xe0
[    3.571898]  ? __x64_sys_openat+0x9d/0x110
[    3.571899]  ? do_syscall_64+0xee/0x500
[    3.571901]  ? entry_SYSCALL_64_after_hwframe+0x77/0x7f
[    3.571902]  ? __pfx_path_openat+0x10/0x10
[    3.571905]  ? kasan_save_stack+0x34/0x50
[    3.571906]  ? kasan_save_stack+0x24/0x50
[    3.571907]  ? mutex_unlock+0x82/0xd0
[    3.571909]  ? __pfx_mutex_unlock+0x10/0x10
[    3.571911]  ? _raw_spin_lock_irqsave+0x8b/0xf0
[    3.571913]  ? gpio_sim_apply_pull+0x1c8/0x4e0
[    3.571915]  ? __pfx_gpio_sim_apply_pull+0x10/0x10
[    3.571917]  ? kasan_save_track+0x14/0x30
[    3.571918]  kasan_save_track+0x14/0x30
[    3.571920]  kasan_save_free_info+0x3a/0x60
[    3.571921]  __kasan_slab_free+0x43/0x70
[    3.571923]  kfree+0x18e/0x3c0
[    3.571925]  ? __pfx_sysfs_kf_write+0x10/0x10
[    3.571926]  kernfs_fop_write_iter+0x168/0x480
[    3.571928]  vfs_write+0x87a/0xd40
[    3.571929]  ? alloc_fd+0x2c6/0x5d0
[    3.571932]  ? __pfx_vfs_write+0x10/0x10
[    3.571933]  ? __do_sys_wait4+0xf2/0x100
[    3.571935]  ? fdget_pos+0x1cd/0x4c0
[    3.571937]  ksys_write+0xf3/0x1c0
[    3.571939]  ? __pfx_ksys_write+0x10/0x10
[    3.571940]  do_syscall_64+0xee/0x500
[    3.571942]  entry_SYSCALL_64_after_hwframe+0x77/0x7f
[    3.571944] RIP: 0033:0x49a227
[    3.571945] Code: 64 89 02 48 c7 c0 ff ff ff ff eb bb 0f 1f 80 00 00 00 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 48 89 54 24 18 48 89 74 24
[    3.571947] RSP: 002b:00007ffd89cad1e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[    3.571948] RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 000000000049a227
[    3.571949] RDX: 000000000000000a RSI: 000000003e0afe50 RDI: 0000000000000001
[    3.571951] RBP: 000000003e0afe50 R08: 000000003e0afe50 R09: 006e776f642d6c6c
[    3.571952] R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000000a
[    3.571953] R13: 000000003e0ad8a0 R14: 0000000000609c01 R15: 00007ffd89cad250
[    3.571955]  </TASK>
[    3.571955] 
[    3.571956] Allocated by task 86:
[    3.571957]  kasan_save_stack+0x24/0x50
[    3.571959]  kasan_save_track+0x14/0x30
[    3.571960]  __kasan_kmalloc+0x7f/0x90
[    3.571961]  __kmalloc_node_track_caller_noprof+0x1d4/0x4a0
[    3.571963]  devm_kmalloc+0x81/0x240
[    3.571965]  gpio_vbus_probe+0x30/0x670 [phy_gpio_vbus_usb]
[    3.571968]  platform_probe+0x9e/0x140
[    3.571970]  really_probe+0x1cf/0x5c0
[    3.571972]  __driver_probe_device+0x1a1/0x3b0
[    3.571974]  driver_probe_device+0x49/0xd0
[    3.571975]  __device_attach_driver+0x183/0x200
[    3.571977]  bus_for_each_drv+0x105/0x190
[    3.571979]  __device_attach+0x20b/0x380
[    3.571981]  device_initial_probe+0x7d/0xa0
[    3.571982]  bus_probe_device+0x5a/0x130
[    3.571983]  device_add+0xd6f/0x14c0
[    3.571984]  platform_device_add+0x253/0x5a0
[    3.571986]  platform_device_register_full+0x3c3/0x560
[    3.571988]  0xffffffffc02250aa
[    3.571989]  do_one_initcall+0x89/0x350
[    3.571990]  do_init_module+0x2a1/0x890
[    3.571992]  load_module+0x5166/0x6750
[    3.571994]  init_module_from_file+0x162/0x190
[    3.571996]  idempotent_init_module+0x325/0x680
[    3.571997]  __x64_sys_finit_module+0xc2/0x130
[    3.571999]  do_syscall_64+0xee/0x500
[    3.572001]  entry_SYSCALL_64_after_hwframe+0x77/0x7f
[    3.572002] 
[    3.572002] Freed by task 91:
[    3.572003]  kasan_save_stack+0x24/0x50
[    3.572004]  kasan_save_track+0x14/0x30
[    3.572005]  kasan_save_free_info+0x3a/0x60
[    3.572007]  __kasan_slab_free+0x43/0x70
[    3.572008]  kfree+0x18e/0x3c0
[    3.572009]  release_nodes+0xbe/0x120
[    3.572011]  devres_release_all+0x127/0x1a0
[    3.572012]  device_unbind_cleanup+0x76/0x260
[    3.572014]  device_release_driver_internal+0x163/0x210
[    3.572015]  bus_remove_device+0x256/0x3e0
[    3.572017]  device_del+0x3a8/0x960
[    3.572019]  platform_device_del.part.0+0x1f/0x1e0
[    3.572020]  platform_device_unregister+0x20/0x40
[    3.572022]  0xffffffffc022008c
[    3.572023]  __x64_sys_delete_module+0x32c/0x4a0
[    3.572025]  do_syscall_64+0xee/0x500
[    3.572026]  entry_SYSCALL_64_after_hwframe+0x77/0x7f
[    3.572027] 
[    3.572028] Last potentially related work creation:
[    3.572028]  kasan_save_stack+0x24/0x50
[    3.572029]  kasan_record_aux_stack+0x89/0xa0
[    3.572031]  insert_work+0x2d/0x240
[    3.572033]  __queue_work+0x44e/0xd70
[    3.572034]  call_timer_fn+0x27/0x210
[    3.572035]  __run_timer_base.part.0+0x3cc/0x900
[    3.572037]  run_timer_softirq+0xd6/0x190
[    3.572039]  handle_softirqs+0x184/0x5c0
[    3.572040]  irq_exit_rcu+0x6e/0x150
[    3.572041]  sysvec_apic_timer_interrupt+0x70/0x80
[    3.572042]  asm_sysvec_apic_timer_interrupt+0x1a/0x20
[    3.572044] 
[    3.572044] Second to last potentially related work creation:
[    3.572045]  kasan_save_stack+0x24/0x50
[    3.572046]  kasan_record_aux_stack+0x89/0xa0
[    3.572047]  insert_work+0x2d/0x240
[    3.572048]  __queue_work+0x44e/0xd70
[    3.572050]  call_timer_fn+0x27/0x210
[    3.572051]  __run_timer_base.part.0+0x3cc/0x900
[    3.572052]  run_timer_softirq+0xd6/0x190
[    3.572054]  handle_softirqs+0x184/0x5c0
[    3.572055]  irq_exit_rcu+0x6e/0x150
[    3.572056]  sysvec_apic_timer_interrupt+0x39/0x80
[    3.572058]  asm_sysvec_apic_timer_interrupt+0x1a/0x20
[    3.572059] 
[    3.572059] The buggy address belongs to the object at ffff888003329000
[    3.572059]  which belongs to the cache kmalloc-1k of size 1024
[    3.572061] The buggy address is located 472 bytes inside of
[    3.572061]  freed 1024-byte region [ffff888003329000, ffff888003329400)
[    3.572062] 
[    3.572063] The buggy address belongs to the physical page:
[    3.572064] page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff888003328000 pfn:0x3328
[    3.572066] head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
[    3.572067] flags: 0x100000000000240(workingset|head|node=0|zone=1)
[    3.572069] page_type: f5(slab)
[    3.572071] raw: 0100000000000240 ffff888001041dc0 ffff888001040590 ffffea0000110610
[    3.572073] raw: ffff888003328000 000000000010000f 00000000f5000000 0000000000000000
[    3.572075] head: 0100000000000240 ffff888001041dc0 ffff888001040590 ffffea0000110610
[    3.572076] head: ffff888003328000 000000000010000f 00000000f5000000 0000000000000000
[    3.572077] head: 0100000000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
[    3.572078] head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
[    3.572078] page dumped because: kasan: bad access detected
[    3.572079] 
[    3.572079] Memory state around the buggy address:
[    3.572080]  ffff888003329080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[    3.572081]  ffff888003329100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[    3.572082] >ffff888003329180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[    3.572083]                                                     ^
[    3.572084]  ffff888003329200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[    3.572084]  ffff888003329280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[    3.572085] ==================================================================

(The "gpiod_get_value can_sleep" WARNINGs earlier in the boot are a
gpio-sim artifact - simulated chips set can_sleep - and are unrelated
to the bug.  One of the five runs faulted in gpio_vbus_work() itself
instead of __run_timer_base(); same object, same free site.)

Reproducer kit (against the KASAN kernel tree above):

vbus_rig.c:

// SPDX-License-Identifier: GPL-2.0
/*
 * vbus_rig - PoC rig for the gpio-vbus teardown UAF (F-138).
 *
 * Instantiates a "gpio-vbus" platform device wired via a gpiod lookup
 * table to line 0 of a gpio-sim chip labelled "vbus-sim", so the real
 * phy-gpio-vbus-usb platform driver probes it.  Attaches a dummy
 * usb_gadget to phy->otg->gadget so the driver's IRQ handler takes its
 * normal schedule_delayed_work() path (it skips scheduling when no
 * gadget is attached - on real hardware a UDC provides the gadget).
 * rmmod vbus_rig runs the real gpio_vbus_remove() path.  Contains no
 * vulnerable logic itself.
 */
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/gpio/machine.h>
#include <linux/usb/phy.h>
#include <linux/usb/gadget.h>
#include <linux/usb/otg.h>

static struct gpiod_lookup_table vbus_lookup = {
	.dev_id = "gpio-vbus.0",
	.table = {
		GPIO_LOOKUP("vbus-sim", 0, "vbus", GPIO_ACTIVE_HIGH),
		{ }
	},
};

static const struct usb_gadget_ops vbus_rig_gadget_ops; /* all NULL */
static struct usb_gadget vbus_rig_gadget = {
	.ops	= (struct usb_gadget_ops *)&vbus_rig_gadget_ops,
	.name	= "vbus_rig",
};

static struct platform_device *vbus_pdev;
static struct usb_phy *rig_phy;

static int __init vbus_rig_init(void)
{
	gpiod_add_lookup_table(&vbus_lookup);
	vbus_pdev = platform_device_register_simple("gpio-vbus", 0, NULL, 0);
	if (IS_ERR(vbus_pdev)) {
		gpiod_remove_lookup_table(&vbus_lookup);
		return PTR_ERR(vbus_pdev);
	}

	rig_phy = usb_get_phy(USB_PHY_TYPE_USB2);
	if (IS_ERR(rig_phy)) {
		pr_err("vbus_rig: no phy found (%ld) - setup broken\n",
		       PTR_ERR(rig_phy));
		goto fail;
	}
	if (!rig_phy->otg) {
		pr_err("vbus_rig: phy has no otg - setup broken\n");
		usb_put_phy(rig_phy);
		goto fail;
	}
	rig_phy->otg->gadget = &vbus_rig_gadget;
	pr_info("vbus_rig: gpio-vbus.0 registered, phy attached\n");
	return 0;

fail:
	platform_device_unregister(vbus_pdev);
	gpiod_remove_lookup_table(&vbus_lookup);
	return -ENODEV;
}

static void __exit vbus_rig_exit(void)
{
	/*
	 * Drop our phy reference first; the driver module stays put via
	 * the bound device.  Keep the gadget attached across the
	 * unregister: the driver's IRQ handler must keep taking its
	 * normal schedule_delayed_work() path all the way through
	 * remove().
	 */
	usb_put_phy(rig_phy);
	platform_device_unregister(vbus_pdev);
	gpiod_remove_lookup_table(&vbus_lookup);
	pr_info("vbus_rig: gpio-vbus.0 unregistered\n");
}

module_init(vbus_rig_init);
module_exit(vbus_rig_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("gpio-vbus teardown UAF PoC rig");

Makefile:

obj-m += vbus_rig.o

guest init script (packed into a busybox initramfs with udc-core.ko,
phy-gpio-vbus-usb.ko and vbus_rig.ko):

#!/bin/sh
# PoC init: gpio-vbus teardown re-arm UAF (F-138)
#
# mode=vuln    : kernel has the unpatched gpio_vbus_remove() + a 500ms
#                POC-WITNESS msleep() after cancel_delayed_work_sync().
# mode=fixed   : kernel has the fix (devm_free_irq before the cancel)
#                plus the same witness sleep.
#
# A busy toggler flips the gpio-sim line pull (= VBUS edges) while
# rmmod runs the real remove path.  In vuln mode an edge lands after
# the cancel, re-arms the 100ms debounce work, and the work fires on
# the freed gpio_vbus_data -> KASAN slab-use-after-free.
#
# The toggler prints nothing; the console between "rmmod starts" and
# the verdict carries only kernel output.  If a run comes out clean,
# just run it again (IRQ delivery timing varies).
mount -t proc proc /proc
mount -t sysfs sysfs /sys
mount -t devtmpfs dev /dev
mount -t configfs none /sys/kernel/config

# 1. one-line gpio-sim chip labelled "vbus-sim"
SIM=/sys/kernel/config/gpio-sim/sim0
mkdir -p $SIM/bank0
echo vbus-sim > $SIM/bank0/label
echo 1 > $SIM/bank0/num_lines
echo 1 > $SIM/live
PULL=$(echo /sys/devices/platform/gpio-sim.0/gpiochip*/sim_gpio0/pull)

# 2. load the gadget core, the real driver + rig (probe runs now)
insmod /udc-core.ko || { echo "SETUP FAIL: udc-core"; poweroff -f; }
insmod /phy-gpio-vbus-usb.ko || { echo "SETUP FAIL: phy module"; poweroff -f; }
insmod /vbus_rig.ko || { echo "SETUP FAIL: rig (phy attach broken)"; poweroff -f; }
ls /sys/bus/platform/drivers/gpio-vbus/
grep -i vbus /proc/interrupts || { echo "SETUP FAIL: no vbus irq"; poweroff -f; }

# 3. toggle VBUS edges at max rate, then run the real remove path
( while :; do echo pull-up > $PULL; echo pull-down > $PULL; done ) &
T=$!
sleep 1
echo "=== rmmod vbus_rig: remove path ==="
rmmod vbus_rig
sleep 2
kill $T

# 4. verdict
if dmesg | grep -q 'BUG: KASAN'; then
	echo "=== RESULT: KASAN SPLAT (vuln confirmed) ==="
else
	echo "=== RESULT: clean (no KASAN splat) ==="
fi
poweroff -f

run.sh (QEMU wrapper; its first argument is only a log label, the
vulnerable/fixed state comes from which witness diff was applied at
build time):

#!/bin/bash
# run.sh -- boot the PoC in QEMU.  usage: run.sh <label> [logfile]
#
# NOTE: <label> is only a name for the log; it does NOT switch kernel
# state.  The vulnerable/fixed state comes from which witness diff is
# applied to the kernel tree when the modules and initramfs were last
# built (see README.md: vuln = witness-vuln.diff, fixed =
# witness-fixed.diff).
set -o pipefail
cd "$(dirname "$0")"
K=${KDIR:-$HOME/patternmine/worktrees/vm-hdlc}
MODE=${1:-vuln}
LOG=${2:-/tmp/f138-$MODE.log}

timeout 120 qemu-system-x86_64 -enable-kvm -cpu host -smp 2 -m 1024 \
	-kernel "$K/arch/x86/boot/bzImage" \
	-initrd initramfs.cpio \
	-append "console=ttyS0 loglevel=8 panic_on_oops=0" \
	-nographic -no-reboot 2>&1 | tee "$LOG"

matrix.sh (repeated runs):

#!/bin/bash
# matrix.sh -- run N VMs with the current build, print the tally.
# usage: matrix.sh <N> <label>   (label is only for log naming; the
# vulnerable/fixed state comes from which witness diff was applied at
# build time -- see README.md)
cd "$(dirname "$0")"
N=${1:-5}
MODE=${2:-vuln}
HIT=0
for i in $(seq 1 "$N"); do
	./run.sh "$MODE" "/tmp/f138-matrix-$MODE-$i.log" >/dev/null 2>&1
	if grep -q 'BUG: KASAN' "/tmp/f138-matrix-$MODE-$i.log"; then
		HIT=$((HIT+1))
	elif grep -q 'SETUP FAIL' "/tmp/f138-matrix-$MODE-$i.log"; then
		echo "run $i: SETUP FAIL - do not count"; continue
	fi
	echo "run $i: $(grep -m1 'RESULT' "/tmp/f138-matrix-$MODE-$i.log" | sed 's/.*=== //;s/ ===//')"
done
echo "== $MODE: $HIT/$N KASAN splats =="

witness diff applied to the vulnerable kernel (window widening only,
logic unchanged):

diff --git a/drivers/usb/phy/phy-gpio-vbus-usb.c b/drivers/usb/phy/phy-gpio-vbus-usb.c
index ce09e789afd8..f3e1c3f3b125 100644
--- a/drivers/usb/phy/phy-gpio-vbus-usb.c
+++ b/drivers/usb/phy/phy-gpio-vbus-usb.c
@@ -332,6 +332,12 @@ static void gpio_vbus_remove(struct platform_device *pdev)
 	device_init_wakeup(&pdev->dev, 0);
 	cancel_delayed_work_sync(&gpio_vbus->work);
 
+	/* POC-WITNESS: widen the re-arm window so the reproducer's
+	 * interrupt lands reliably between the cancel and the devm
+	 * release.  Not part of the bug; logic unchanged.
+	 */
+	msleep(500);
+
 	usb_remove_phy(&gpio_vbus->phy);
 }

and for the patched control run, the fix plus the same window:

diff --git a/drivers/usb/phy/phy-gpio-vbus-usb.c b/drivers/usb/phy/phy-gpio-vbus-usb.c
index ce09e789afd8..25e0dcd36b34 100644
--- a/drivers/usb/phy/phy-gpio-vbus-usb.c
+++ b/drivers/usb/phy/phy-gpio-vbus-usb.c
@@ -330,8 +330,15 @@ static void gpio_vbus_remove(struct platform_device *pdev)
 	struct gpio_vbus_data *gpio_vbus = platform_get_drvdata(pdev);
 
 	device_init_wakeup(&pdev->dev, 0);
+
+	devm_free_irq(&pdev->dev, gpio_vbus->irq, pdev);
 	cancel_delayed_work_sync(&gpio_vbus->work);
 
+	/* POC-WITNESS: same artificial window as the vuln run, to show
+	 * the fix closes it.
+	 */
+	msleep(500);
+
 	usb_remove_phy(&gpio_vbus->phy);
 }