linux-kernel - Re: [PATCH] iio: adc: meson-saradc: Variables could be uninitalized if regmap

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Date:   Sat, 28 Sep 2019 08:47:20 +0200
From:   Nicholas Mc Guire <der.herr@...r.at>
To:     Yizhuo <yzhai003@....edu>
Cc:     csong@...ucr.edu, zhiyunq@...ucr.edu,
        Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Kevin Hilman <khilman@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Nicholas Mc Guire <hofrat@...dl.org>,
        linux-iio@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: adc: meson-saradc: Variables could be uninitalized
 if regmap_read() fails

On Fri, Sep 27, 2019 at 05:46:41PM -0700, Yizhuo wrote:
> Several functions in this file are trying to use regmap_read() to
> initialize the specific variable, however, if regmap_read() fails,
> the variable could be uninitialized but used directly, which is
> potentially unsafe. The return value of regmap_read() should be
> checked and handled.
> 
> Signed-off-by: Yizhuo <yzhai003@....edu>

Just a few minor style issues - contentwise it look correct to me.
Reviewed-by: Nicholas Mc Guire <hofrat@...dl.org>

> ---
>  drivers/iio/adc/meson_saradc.c | 28 +++++++++++++++++++++++-----
>  1 file changed, 23 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/iio/adc/meson_saradc.c b/drivers/iio/adc/meson_saradc.c
> index 7b28d045d271..c032a64108b4 100644
> --- a/drivers/iio/adc/meson_saradc.c
> +++ b/drivers/iio/adc/meson_saradc.c
> @@ -323,6 +323,7 @@ static int meson_sar_adc_wait_busy_clear(struct iio_dev *indio_dev)
>  {
>  	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
>  	int regval, timeout = 10000;
> +	int ret;
>  
>  	/*
>  	 * NOTE: we need a small delay before reading the status, otherwise
> @@ -331,7 +332,9 @@ static int meson_sar_adc_wait_busy_clear(struct iio_dev *indio_dev)
>  	 */
>  	do {
>  		udelay(1);
> -		regmap_read(priv->regmap, MESON_SAR_ADC_REG0, &regval);
> +		ret = regmap_read(priv->regmap, MESON_SAR_ADC_REG0, &regval);
> +		if (ret)
> +			return ret;
>  	} while (FIELD_GET(MESON_SAR_ADC_REG0_BUSY_MASK, regval) && timeout--);
>  
>  	if (timeout < 0)
> @@ -358,7 +361,11 @@ static int meson_sar_adc_read_raw_sample(struct iio_dev *indio_dev,

any reason not to declear ret in the declaration block ?
so just for consistency with coding style within meson_saradc.c
this might be:

	int regval, fifo_chan, fifo_val, count;
+	int ret;

>  		return -EINVAL;
>  	}
>  
> -	regmap_read(priv->regmap, MESON_SAR_ADC_FIFO_RD, &regval);
> +	int ret = regmap_read(priv->regmap, MESON_SAR_ADC_FIFO_RD, &regval);

+	ret = regmap_read(priv->regmap, MESON_SAR_ADC_FIFO_RD, &regval);

> +
> +	if (ret)
> +		return ret;
> +
>  	fifo_chan = FIELD_GET(MESON_SAR_ADC_FIFO_RD_CHAN_ID_MASK, regval);
>  	if (fifo_chan != chan->address) {
>  		dev_err(&indio_dev->dev,
> @@ -491,6 +498,7 @@ static int meson_sar_adc_lock(struct iio_dev *indio_dev)
>  {
>  	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
>  	int val, timeout = 10000;
> +	int ret;
>  
>  	mutex_lock(&indio_dev->mlock);
>  
> @@ -506,7 +514,10 @@ static int meson_sar_adc_lock(struct iio_dev *indio_dev)
>  		 */
>  		do {
>  			udelay(1);
> -			regmap_read(priv->regmap, MESON_SAR_ADC_DELAY, &val);
> +			ret = regmap_read(priv->regmap,
> +					MESON_SAR_ADC_DELAY, &val);

checkpatch does not fuss here but the continuation should be alligned
witht the ( here

> +			if (ret)
> +				return ret;
>  		} while (val & MESON_SAR_ADC_DELAY_BL30_BUSY && timeout--);
>  
>  		if (timeout < 0) {
> @@ -784,7 +795,10 @@ static int meson_sar_adc_init(struct iio_dev *indio_dev)
>  		 * BL30 to make sure BL30 gets the values it expects when
>  		 * reading the temperature sensor.
>  		 */
> -		regmap_read(priv->regmap, MESON_SAR_ADC_REG3, &regval);
> +		ret = regmap_read(priv->regmap, MESON_SAR_ADC_REG3, &regval);
> +		if (ret)
> +			return ret;
> +
>  		if (regval & MESON_SAR_ADC_REG3_BL30_INITIALIZED)
>  			return 0;
>  	}
> @@ -1014,7 +1028,11 @@ static irqreturn_t meson_sar_adc_irq(int irq, void *data)
>  	unsigned int cnt, threshold;
>  	u32 regval;

same as above

+       int ret;

>  
> -	regmap_read(priv->regmap, MESON_SAR_ADC_REG0, &regval);
> +	int ret = regmap_read(priv->regmap, MESON_SAR_ADC_REG0, &regval);

+	ret = regmap_read(priv->regmap, MESON_SAR_ADC_REG0, &regval);

> +
> +	if (ret)
> +		return ret;
> +
>  	cnt = FIELD_GET(MESON_SAR_ADC_REG0_FIFO_COUNT_MASK, regval);
>  	threshold = FIELD_GET(MESON_SAR_ADC_REG0_FIFO_CNT_IRQ_MASK, regval);
>  
> -- 
> 2.17.1
>