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usb: gadget: at91_udc: drain polled-VBUS timer/work before udc is freed

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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: 4037242c4f ("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 <fanwu01@zju.edu.cn>
Link: https://patch.msgid.link/20260719042839.3167094-1-fanwu01@zju.edu.cn
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Fan Wu 2026-07-19 04:28:39 +00:00 committed by Greg Kroah-Hartman
parent 0f6bffb500
commit c27d13ce4b
1 changed files with 19 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
drivers/usb/gadget/udc/at91_udc.c
View File

@ -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");