linux-kernel - Re: [PATCH] iio: adc: stm32: add check on clock rate

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Date:   Sat, 21 Oct 2017 17:55:40 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Fabrice Gasnier <fabrice.gasnier@...com>
Cc:     <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <mcoquelin.stm32@...il.com>,
        <alexandre.torgue@...com>, <benjamin.gaignard@...com>,
        <benjamin.gaignard@...aro.org>, <linux-iio@...r.kernel.org>,
        <lars@...afoo.de>, <knaack.h@....de>, <pmeerw@...erw.net>
Subject: Re: [PATCH] iio: adc: stm32: add check on clock rate

On Wed, 18 Oct 2017 13:40:12 +0200
Fabrice Gasnier <fabrice.gasnier@...com> wrote:

> Add check on STM32 ADC clock rate to report an explicit error.
> This may avoid division by 0 later in stm32-adc driver.
> 
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@...com>
I've applied this via the slow path for the next merge window as you haven't
explicitly highlighted it as a fix.  If you want it to go through for stable
etc then let me know...

I have no idea if this can be triggered in sensibly configured system or not!

Thanks,

Jonathan

> ---
>  drivers/iio/adc/stm32-adc-core.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/drivers/iio/adc/stm32-adc-core.c b/drivers/iio/adc/stm32-adc-core.c
> index 804198e..6aefef9 100644
> --- a/drivers/iio/adc/stm32-adc-core.c
> +++ b/drivers/iio/adc/stm32-adc-core.c
> @@ -139,6 +139,11 @@ static int stm32f4_adc_clk_sel(struct platform_device *pdev,
>  	}
>  
>  	rate = clk_get_rate(priv->aclk);
> +	if (!rate) {
> +		dev_err(&pdev->dev, "Invalid clock rate: 0\n");
> +		return -EINVAL;
> +	}
> +
>  	for (i = 0; i < ARRAY_SIZE(stm32f4_pclk_div); i++) {
>  		if ((rate / stm32f4_pclk_div[i]) <= STM32F4_ADC_MAX_CLK_RATE)
>  			break;
> @@ -216,6 +221,10 @@ static int stm32h7_adc_clk_sel(struct platform_device *pdev,
>  		 * From spec: PLL output musn't exceed max rate
>  		 */
>  		rate = clk_get_rate(priv->aclk);
> +		if (!rate) {
> +			dev_err(&pdev->dev, "Invalid adc clock rate: 0\n");
> +			return -EINVAL;
> +		}
>  
>  		for (i = 0; i < ARRAY_SIZE(stm32h7_adc_ckmodes_spec); i++) {
>  			ckmode = stm32h7_adc_ckmodes_spec[i].ckmode;
> @@ -232,6 +241,10 @@ static int stm32h7_adc_clk_sel(struct platform_device *pdev,
>  
>  	/* Synchronous clock modes (e.g. ckmode is 1, 2 or 3) */
>  	rate = clk_get_rate(priv->bclk);
> +	if (!rate) {
> +		dev_err(&pdev->dev, "Invalid bus clock rate: 0\n");
> +		return -EINVAL;
> +	}
>  
>  	for (i = 0; i < ARRAY_SIZE(stm32h7_adc_ckmodes_spec); i++) {
>  		ckmode = stm32h7_adc_ckmodes_spec[i].ckmode;