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

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Date:   Tue, 1 Oct 2019 10:18:21 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Yizhuo <yzhai003@....edu>
Cc:     csong@...ucr.edu, zhiyunq@...ucr.edu,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        bcm-kernel-feedback-list@...adcom.com,
        Stephen Boyd <swboyd@...omium.org>,
        Allison Randal <allison@...utok.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-iio@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: adc: Variables could be uninitalized if
 regmap_read() fails

On Sun, 29 Sep 2019 22:25:39 -0700
Yizhuo <yzhai003@....edu> 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>
I haven't checked if this one has a clock, but there is a bigger issue.
See inline.

Jonathan

> ---
>  drivers/iio/adc/bcm_iproc_adc.c | 45 ++++++++++++++++++++++++++++-----
>  1 file changed, 39 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/iio/adc/bcm_iproc_adc.c b/drivers/iio/adc/bcm_iproc_adc.c
> index 646ebdc0a8b4..6df19ceb5ff2 100644
> --- a/drivers/iio/adc/bcm_iproc_adc.c
> +++ b/drivers/iio/adc/bcm_iproc_adc.c
> @@ -137,6 +137,7 @@ static irqreturn_t iproc_adc_interrupt_thread(int irq, void *data)
>  	u32 channel_intr_status;
>  	u32 intr_status;
>  	u32 intr_mask;
> +	int ret;
>  	struct iio_dev *indio_dev = data;
>  	struct iproc_adc_priv *adc_priv = iio_priv(indio_dev);
>  
> @@ -145,8 +146,19 @@ static irqreturn_t iproc_adc_interrupt_thread(int irq, void *data)
>  	 * Make sure this interrupt is intended for us.
>  	 * Handle only ADC channel specific interrupts.
>  	 */
> -	regmap_read(adc_priv->regmap, IPROC_INTERRUPT_STATUS, &intr_status);
> -	regmap_read(adc_priv->regmap, IPROC_INTERRUPT_MASK, &intr_mask);
> +	ret = regmap_read(adc_priv->regmap,
> +					IPROC_INTERRUPT_STATUS, &intr_status);
> +	if (ret) {
> +		dev_err(&indio_dev->dev, "Fail to read IPROC_INTERRUPT_STATUS.\n");
> +		return ret;
> +	}
> +
> +	ret = regmap_read(adc_priv->regmap, IPROC_INTERRUPT_MASK, &intr_mask);
> +	if (ret) {
> +		dev_err(&indio_dev->dev, "Fail to read IPROC_INTERRUPT_MASK.\n");
> +		return ret;
> +	}
You need to be extremely careful returning error codes from interrupt routines..

Basically you can't ;)

> +
>  	intr_status = intr_status & intr_mask;
>  	channel_intr_status = (intr_status & IPROC_ADC_INTR_MASK) >>
>  				IPROC_ADC_INTR;
> @@ -162,6 +174,7 @@ static irqreturn_t iproc_adc_interrupt_handler(int irq, void *data)
>  	struct iproc_adc_priv *adc_priv;
>  	struct iio_dev *indio_dev = data;
>  	unsigned int valid_entries;
> +	int ret;
>  	u32 intr_status;
>  	u32 intr_channels;
>  	u32 channel_status;
> @@ -169,23 +182,37 @@ static irqreturn_t iproc_adc_interrupt_handler(int irq, void *data)
>  
>  	adc_priv = iio_priv(indio_dev);
>  
> -	regmap_read(adc_priv->regmap, IPROC_INTERRUPT_STATUS, &intr_status);
> +	ret = regmap_read(adc_priv->regmap,
> +					IPROC_INTERRUPT_STATUS, &intr_status);
> +	if (ret) {
> +		dev_err(&indio_dev->dev, "Fail to read IPROC_INTERRUPT_STATUS.\n");
> +		return ret;
> +	}
> +
>  	dev_dbg(&indio_dev->dev, "iproc_adc_interrupt_handler(),INTRPT_STS:%x\n",
>  			intr_status);
>  
>  	intr_channels = (intr_status & IPROC_ADC_INTR_MASK) >> IPROC_ADC_INTR;
>  	if (intr_channels) {
> -		regmap_read(adc_priv->regmap,
> +		ret = regmap_read(adc_priv->regmap,
>  			    IPROC_ADC_CHANNEL_INTERRUPT_STATUS +
>  			    IPROC_ADC_CHANNEL_OFFSET * adc_priv->chan_id,
>  			    &ch_intr_status);
> +		if (ret) {
> +			dev_err(&indio_dev->dev, "Fail to read the register.\n");
> +			return ret;
> +		}
>  
>  		if (ch_intr_status & IPROC_ADC_CHANNEL_WTRMRK_INTR_MASK) {
> -			regmap_read(adc_priv->regmap,
> +			ret = regmap_read(adc_priv->regmap,
>  					IPROC_ADC_CHANNEL_STATUS +
>  					IPROC_ADC_CHANNEL_OFFSET *
>  					adc_priv->chan_id,
>  					&channel_status);
> +			if (ret) {
> +				dev_err(&indio_dev->dev, "Fail to read the register.\n");
> +				return ret;
> +			}
>  
>  			valid_entries = ((channel_status &
>  				IPROC_ADC_CHANNEL_VALID_ENTERIES_MASK) >>
> @@ -230,6 +257,7 @@ static int iproc_adc_do_read(struct iio_dev *indio_dev,
>  	u32 mask;
>  	u32 val_check;
>  	int failed_cnt = 0;
> +	int ret;
>  	struct iproc_adc_priv *adc_priv = iio_priv(indio_dev);
>  
>  	mutex_lock(&adc_priv->mutex);
> @@ -284,7 +312,12 @@ static int iproc_adc_do_read(struct iio_dev *indio_dev,
>  	 * Testing has shown that this may loop a few time, but we have never
>  	 * hit the full count.
>  	 */
> -	regmap_read(adc_priv->regmap, IPROC_INTERRUPT_MASK, &val_check);
> +	ret = regmap_read(adc_priv->regmap, IPROC_INTERRUPT_MASK, &val_check);
> +	if (ret) {
> +		dev_err(&indio_dev->dev, "Fail to read IPROC_INTERRUPT_MASK.\n");
> +		return ret;
> +	}
> +
>  	while (val_check != val) {
>  		failed_cnt++;
>