Re: [PATCH v2 5/6] media: mediatek: vpu: Use devm_of_reserved_mem_device_init()

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] Pre-existing race condition leading to a use-after-free. The driver uses `devm_request_irq()` to manage its interrupt, but manually destroys the workqueue (`vpu->wdt.wq`) in `mtk_vpu_remove()`. Because devres cleans up the IRQ only after `remove()` completes, the interrupt remains active while the workqueue is freed.
--

commit 246438dea9de2810275787060608206f1c3a4872
Author: Mukesh Ojha <mukesh.ojha@oss.qualcomm.com>

media: mediatek: vpu: Use devm_of_reserved_mem_device_init()

This patch simplifies the driver by replacing manual
of_reserved_mem_device_init() and of_reserved_mem_device_release()
calls with the managed devm_of_reserved_mem_device_init() equivalent.

> diff --git a/drivers/media/platform/mediatek/vpu/mtk_vpu.c b/drivers/media/platform/mediatek/vpu/mtk_vpu.c
> --- a/drivers/media/platform/mediatek/vpu/mtk_vpu.c
> +++ b/drivers/media/platform/mediatek/vpu/mtk_vpu.c
[ ... ]
> @@ -930,7 +930,6 @@ static int mtk_vpu_probe(struct platform_device *pdev)
>  free_d_mem:
>  	vpu_free_ext_mem(vpu, D_FW);
>  remove_debugfs:
> -	of_reserved_mem_device_release(dev);

[Severity: High]
This is a pre-existing issue, but while reviewing this devres conversion, I
noticed a potential use-after-free race condition related to device teardown.

In mtk_vpu_probe(), the interrupt is registered as managed using
devm_request_irq(), meaning it will remain active until devres cleanup runs
after mtk_vpu_remove() completes.

However, the workqueue is manually destroyed during mtk_vpu_remove():

drivers/media/platform/mediatek/vpu/mtk_vpu.c:mtk_vpu_remove() {
    ...
    if (vpu->wdt.wq)
        destroy_workqueue(vpu->wdt.wq);
    ...
}

If a hardware interrupt fires after destroy_workqueue() executes but before
the devres cleanup disables the IRQ, vpu_irq_handler() will attempt to
access the freed workqueue structure:

drivers/media/platform/mediatek/vpu/mtk_vpu.c:vpu_irq_handler() {
    ...
    queue_work(vpu->wdt.wq, &vpu->wdt.ws);
    ...
}

Can this sequence cause a use-after-free if the hardware triggers an
interrupt late during the unbind process?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260902200703.2016410-1-mukesh.ojha@oss.qualcomm.com?part=5