linux-kernel - Re: [PATCH] media: allegro: request irq after initializing mbox

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Message-ID: <20210823075353.GC28846@pengutronix.de>
Date:   Mon, 23 Aug 2021 09:53:53 +0200
From:   Michael Tretter <m.tretter@...gutronix.de>
To:     Nadezda Lutovinova <lutovinova@...ras.ru>
Cc:     Pengutronix Kernel Team <kernel@...gutronix.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        ldv-project@...uxtesting.org
Subject: Re: [PATCH] media: allegro: request irq after initializing
 mbox_status

Hi Nadezda,

On Thu, 19 Aug 2021 18:49:35 +0300, Nadezda Lutovinova wrote:
> If IRQ occurs between calling  devm_request_threaded_irq() and
> allegro_firmware_request_nowait(), then null pointer dereference
> occurs since dev->mbox_status wasn't initialized yet but used
> in allegro_mbox_notify(). 

Thanks for the patch. As explained in [0], this is not an issue.

> 
> The patch puts registration of the interrupt handler after
> initializing of neccesery data.

The interrupt handler must be registered during the execution of
allegro_fw_callback(), because the driver exchanges messages with the firmware
during the bring up. With this patch this is not guaranteed anymore.

Michael

[0] https://lore.kernel.org/linux-media/20210511072834.GC17882@pengutronix.de/

> 
> Found by Linux Driver Verification project (linuxtesting.org).
> 
> Signed-off-by: Nadezda Lutovinova <lutovinova@...ras.ru>
> ---
>  .../media/platform/allegro-dvt/allegro-core.c | 24 +++++++++----------
>  1 file changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/media/platform/allegro-dvt/allegro-core.c b/drivers/media/platform/allegro-dvt/allegro-core.c
> index 887b492e4ad1..9c1997ff74e8 100644
> --- a/drivers/media/platform/allegro-dvt/allegro-core.c
> +++ b/drivers/media/platform/allegro-dvt/allegro-core.c
> @@ -3707,18 +3707,6 @@ static int allegro_probe(struct platform_device *pdev)
>  		return PTR_ERR(dev->sram);
>  	}
>  
> -	irq = platform_get_irq(pdev, 0);
> -	if (irq < 0)
> -		return irq;
> -	ret = devm_request_threaded_irq(&pdev->dev, irq,
> -					allegro_hardirq,
> -					allegro_irq_thread,
> -					IRQF_SHARED, dev_name(&pdev->dev), dev);
> -	if (ret < 0) {
> -		dev_err(&pdev->dev, "failed to request irq: %d\n", ret);
> -		return ret;
> -	}
> -
>  	ret = v4l2_device_register(&pdev->dev, &dev->v4l2_dev);
>  	if (ret)
>  		return ret;
> @@ -3732,6 +3720,18 @@ static int allegro_probe(struct platform_device *pdev)
>  		return ret;
>  	}
>  
> +	irq = platform_get_irq(pdev, 0);
> +	if (irq < 0)
> +		return irq;
> +	ret = devm_request_threaded_irq(&pdev->dev, irq,
> +					allegro_hardirq,
> +					allegro_irq_thread,
> +					IRQF_SHARED, dev_name(&pdev->dev), dev);
> +	if (ret < 0) {
> +		dev_err(&pdev->dev, "failed to request irq: %d\n", ret);
> +		return ret;
> +	}
> +
>  	return 0;
>  }
>  
> -- 
> 2.17.1
> 
>