From c27d13ce4bab80fbdf6523928071b6c24b37606c Mon Sep 17 00:00:00 2001 From: Fan Wu Date: Sun, 19 Jul 2026 04:28:39 +0000 Subject: [PATCH] usb: gadget: at91_udc: drain polled-VBUS timer/work before udc is freed In polled-VBUS mode (board.vbus_pin && board.vbus_polled), probe arms a self-restarting cycle: at91_vbus_timer() schedules vbus_timer_work, and at91_vbus_timer_work() calls at91_vbus_update() and re-arms the timer via mod_timer(). Both recover the same udc through container_of and dereference it on every iteration. Neither teardown path cancels this cycle. udc is devm-allocated, so it is freed after at91udc_remove() returns, and is likewise freed when probe fails and devres runs. A timer callback or work item that is pending or running at either point dereferences the freed udc. Add at91_udc_shutdown_vbus_timer() and call it from at91udc_remove() and from the usb_add_gadget_udc() failure path in probe; the remaining probe error paths fail before the timer is armed. timer_shutdown_sync() waits for a running callback and clears timer->function, which makes the work handler's mod_timer() a permanent no-op; cancel_work_sync() then drains any pending or running work whose re-arm attempt now does nothing. The timer must be shut down first, since cancelling the work alone would let the timer re-queue it. The guard mirrors probe: in IRQ mode the timer and work_struct are never initialized. This does not require a fault; a normal driver unbind can interleave with an already queued work item. This issue was found by an in-house static analysis tool. Fixes: 4037242c4f5f ("ARM: 6209/3: at91_udc: Add vbus polarity and polling mode") Cc: stable@vger.kernel.org Assisted-by: Codex:gpt-5.6 Signed-off-by: Fan Wu Link: https://patch.msgid.link/20260719042839.3167094-1-fanwu01@zju.edu.cn Signed-off-by: Greg Kroah-Hartman --- drivers/usb/gadget/udc/at91_udc.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) diff --git a/drivers/usb/gadget/udc/at91_udc.c b/drivers/usb/gadget/udc/at91_udc.c index 5aa360ba4f03..8e5d7fb71549 100644 --- a/drivers/usb/gadget/udc/at91_udc.c +++ b/drivers/usb/gadget/udc/at91_udc.c @@ -1794,6 +1794,19 @@ static void at91udc_of_init(struct at91_udc *udc, struct device_node *np) udc->caps = match->data; } +/* + * The work handler re-arms this timer, so shut the timer down before + * draining the work; otherwise it restarts the polling cycle. + */ +static void at91_udc_shutdown_vbus_timer(struct at91_udc *udc) +{ + if (!(udc->board.vbus_pin && udc->board.vbus_polled)) + return; + + timer_shutdown_sync(&udc->vbus_timer); + cancel_work_sync(&udc->vbus_timer_work); +} + static int at91udc_probe(struct platform_device *pdev) { struct device *dev = &pdev->dev; @@ -1907,7 +1920,7 @@ static int at91udc_probe(struct platform_device *pdev) } retval = usb_add_gadget_udc(dev, &udc->gadget); if (retval) - goto err_unprepare_iclk; + goto err_shutdown_vbus; dev_set_drvdata(dev, udc); device_init_wakeup(dev, 1); create_debug_file(udc); @@ -1915,6 +1928,8 @@ static int at91udc_probe(struct platform_device *pdev) INFO("%s version %s\n", driver_name, DRIVER_VERSION); return 0; +err_shutdown_vbus: + at91_udc_shutdown_vbus_timer(udc); err_unprepare_iclk: clk_unprepare(udc->iclk); err_unprepare_fclk: @@ -1933,6 +1948,9 @@ static void at91udc_remove(struct platform_device *pdev) DBG("remove\n"); usb_del_gadget_udc(&udc->gadget); + + at91_udc_shutdown_vbus_timer(udc); + if (udc->driver) { dev_err(&pdev->dev, "Driver still in use but removing anyhow\n");