Re: [PATCH] iio: adc: meson-saradc: Variables could be uninitalized if regmap_read() fails

[Yizhuo Zhai <yzhai003@xxxxxxx>]

Hi Nicholas:

Thanks for your feedback, I made changes and submitted new patches
already. Check patch script generated a warning if I strictly align
the parameter with (. I checked other code inside this file and
modified the continuation accordingly.

On Fri, Sep 27, 2019 at 11:47 PM Nicholas Mc Guire <der.herr@xxxxxxx> wrote:
>
> 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@xxxxxxx>
>
> Just a few minor style issues - contentwise it look correct to me.
> Reviewed-by: Nicholas Mc Guire <hofrat@xxxxxxxxx>
>
> > ---
> >  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
> >



-- 
Kind Regards,

Yizhuo Zhai

Computer Science, Graduate Student
University of California, Riverside