Re: [PATCH v2] iio: vadc: Fix potential dereference of NULL pointer

Jonathan Cameron
2022-05-20T17:13:33Z

On Wed, 18 May 2022 22:50:55 -0700
Yongzhi Liu <lyz_cs@pku.edu.cn> wrote:

> The return value of vadc_get_channel() needs to be checked
> to avoid use of NULL pointer. Fix this by adding the null
> pointer check on prop.
>
> Fixes: 0917de94c ("iio: vadc: Qualcomm SPMI PMIC voltage ADC driver")
>
> Signed-off-by: Yongzhi Liu <lyz_cs@pku.edu.cn>
This function has a lot of goto err; where err just results in
a print.

My suggestion is to just drop that print and use
error specific prints as you have done here, then use direct returns.

> ---
> drivers/iio/adc/qcom-spmi-vadc.c | 23 ++++++++++++++++++++++-
> 1 file changed, 22 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iio/adc/qcom-spmi-vadc.c b/drivers/iio/adc/qcom-spmi-vadc.c
> index 34202ba..9fa61fb 100644
> --- a/drivers/iio/adc/qcom-spmi-vadc.c
> +++ b/drivers/iio/adc/qcom-spmi-vadc.c
> @@ -358,14 +358,25 @@ static int vadc_measure_ref_points(struct vadc_priv *vadc)
> vadc->graph[VADC_CALIB_ABSOLUTE].dx = VADC_ABSOLUTE_RANGE_UV;
>
> prop = vadc_get_channel(vadc, VADC_REF_1250MV);
> + if (!prop) {
> + dev_err(vadc->dev, "Please define 1.25V channel\n");
> + ret = -ENODEV;
> + goto err;
> + }
> ret = vadc_do_conversion(vadc, prop, &read_1);
> if (ret)
> goto err;
>
> /* Try with buffered 625mV channel first */
> prop = vadc_get_channel(vadc, VADC_SPARE1);
> - if (!prop)
> + if (!prop) {
> prop = vadc_get_channel(vadc, VADC_REF_625MV);
> + if (!prop) {
> + dev_err(vadc->dev, "Please define 0.625V channel\n");
> + ret = -ENODEV;
> + goto err;
> + }
> + }
>
> ret = vadc_do_conversion(vadc, prop, &read_2);
> if (ret)
> @@ -381,11 +392,21 @@ static int vadc_measure_ref_points(struct vadc_priv *vadc)
>
> /* Ratiometric calibration */
> prop = vadc_get_channel(vadc, VADC_VDD_VADC);
> + if (!prop) {
> + dev_err(vadc->dev, "Please define VDD channel\n");
> + ret = -ENODEV;
> + goto err;
> + }
> ret = vadc_do_conversion(vadc, prop, &read_1);
> if (ret)
> goto err;
>
> prop = vadc_get_channel(vadc, VADC_GND_REF);
> + if (!prop) {
> + dev_err(vadc->dev, "Please define GND channel\n");
> + ret = -ENODEV;
> + goto err;
> + }
> ret = vadc_do_conversion(vadc, prop, &read_2);
> if (ret)
> goto err;