Re: [PATCH v3] iio: vadc: Fix potential dereference of NULL pointer

Jonathan Cameron
2022-05-22T10:52:33Z

On Fri, 20 May 2022 20:35:35 -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 and dropping general error prints.
>
> Fixes: 0917de94c02f ("iio: vadc: Qualcomm SPMI PMIC voltage ADC driver")
> Signed-off-by: Yongzhi Liu <lyz_cs@pku.edu.cn>
Hi,

Heading in the right direction. A few comments inline.

Thanks,

Jonathan

> ---
> drivers/iio/adc/qcom-spmi-vadc.c | 38 ++++++++++++++++++++++++++++----------
> 1 file changed, 28 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/iio/adc/qcom-spmi-vadc.c b/drivers/iio/adc/qcom-spmi-vadc.c
> index 34202ba..43a52b1 100644
> --- a/drivers/iio/adc/qcom-spmi-vadc.c
> +++ b/drivers/iio/adc/qcom-spmi-vadc.c
> @@ -358,22 +358,33 @@ 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;
> + return ret;

return -ENODEV;

Same for the other case below.

> + }
> ret = vadc_do_conversion(vadc, prop, &read_1);
> if (ret)
> - goto err;

Good to add a note to the patch description that
vadc_do_conversion() already provides error prints in at least
some of it's error paths. Thus it is reasonable to drop the
extra reporting in this function.

> + return ret;
>
> /* 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;
> + return ret;
> + }
> + }
>
> ret = vadc_do_conversion(vadc, prop, &read_2);
> if (ret)
> - goto err;
> + return ret;
>
> if (read_1 == read_2) {
> ret = -EINVAL;
> - goto err;
> + return ret;
> }
>
> vadc->graph[VADC_CALIB_ABSOLUTE].dy = read_1 - read_2;
> @@ -381,25 +392,32 @@ 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;
> + return ret;
> + }
> ret = vadc_do_conversion(vadc, prop, &read_1);
> if (ret)
> - goto err;
> + return ret;
>
> prop = vadc_get_channel(vadc, VADC_GND_REF);
> + if (!prop) {
> + dev_err(vadc->dev, "Please define GND channel\n");
> + ret = -ENODEV;
> + return ret;
> + }
> ret = vadc_do_conversion(vadc, prop, &read_2);
> if (ret)
> - goto err;
> + return ret;
>
> if (read_1 == read_2) {
> ret = -EINVAL;
> - goto err;
> + return ret;
> }
>
> vadc->graph[VADC_CALIB_RATIOMETRIC].dy = read_1 - read_2;
> vadc->graph[VADC_CALIB_RATIOMETRIC].gnd = read_2;
> -err:
> - if (ret)
> - dev_err(vadc->dev, "measure reference points failed\n");
>
> return ret;
> }