[PATCH] iio: humidity: hts221: fix division by zero in calibration data parsing

[PATCH] iio: humidity: hts221: fix division by zero in calibration data parsing

[Yang Zi]

hts221_parse_temp_caldata() and hts221_parse_rh_caldata() compute the
sensor slope as ((cal_y1 - cal_y0) * 8000) / (cal_x1 - cal_x0). If the
device reports cal_x1 == cal_x0 the division causes a divide-by-zero
error.

Return -EINVAL when cal_x1 == cal_x0 in both functions before performing
the division.

Signed-off-by: Yang Zi <2959243019@qq.com>
---
diff --git a/drivers/iio/humidity/hts221_core.c b/drivers/iio/humidity/hts221_core.c
index bfeb0a60d3af..7d1f04951d8b 100644
--- a/drivers/iio/humidity/hts221_core.c
+++ b/drivers/iio/humidity/hts221_core.c
@@ -288,6 +288,9 @@ static int hts221_parse_temp_caldata(struct hts221_hw *hw)
         return err;
     cal_x1 = le16_to_cpu(val);
 
+    if (cal_x1 == cal_x0)
+        return -EINVAL;
+
     slope = &hw->sensors[HTS221_SENSOR_T].slope;
     b_gen = &hw->sensors[HTS221_SENSOR_T].b_gen;
 
@@ -327,6 +330,9 @@ static int hts221_parse_rh_caldata(struct hts221_hw *hw)
         return err;
     cal_x1 = le16_to_cpu(val);
 
+    if (cal_x1 == cal_x0)
+        return -EINVAL;
+
     slope = &hw->sensors[HTS221_SENSOR_H].slope;
     b_gen = &hw->sensors[HTS221_SENSOR_H].b_gen;
 

Re: [PATCH] iio: humidity: hts221: fix division by zero in calibration data parsing

[Joshua Crofts]

On Tue, 25 Aug 2026 17:21:10 +0800
Yang Zi <2959243019@qq.com> wrote:

> hts221_parse_temp_caldata() and hts221_parse_rh_caldata() compute the
> sensor slope as ((cal_y1 - cal_y0) * 8000) / (cal_x1 - cal_x0). If the
> device reports cal_x1 == cal_x0 the division causes a divide-by-zero
> error.
> 
> Return -EINVAL when cal_x1 == cal_x0 in both functions before performing
> the division.
> 
> Signed-off-by: Yang Zi <2959243019@qq.com>
> ---
> diff --git a/drivers/iio/humidity/hts221_core.c b/drivers/iio/humidity/hts221_core.c
> index bfeb0a60d3af..7d1f04951d8b 100644
> --- a/drivers/iio/humidity/hts221_core.c
> +++ b/drivers/iio/humidity/hts221_core.c
> @@ -288,6 +288,9 @@ static int hts221_parse_temp_caldata(struct hts221_hw *hw)
>          return err;
>      cal_x1 = le16_to_cpu(val);
>  
> +    if (cal_x1 == cal_x0)
> +        return -EINVAL;
> +
>      slope = &hw->sensors[HTS221_SENSOR_T].slope;
>      b_gen = &hw->sensors[HTS221_SENSOR_T].b_gen;
>  
> @@ -327,6 +330,9 @@ static int hts221_parse_rh_caldata(struct hts221_hw *hw)
>          return err;
>      cal_x1 = le16_to_cpu(val);
>  
> +    if (cal_x1 == cal_x0)
> +        return -EINVAL;
> +
>      slope = &hw->sensors[HTS221_SENSOR_H].slope;
>      b_gen = &hw->sensors[HTS221_SENSOR_H].b_gen;
>  
> 
> 

This definitely needs a Fixes: tag, otherwise LGTM.

Feel free to carry my review tag.

Reviewed-by: Joshua Crofts <joshua.crofts1@gmail.com>

PS, a bit of process info: I noticed Sashiko (sashiko.dev) failed to apply your
patches. To prevent this from happening in the future, please use the `--base` flag
when running `git format-patch` to specify which commit it should be applied onto.

-- 
Kind regards,
Joshua Crofts

Re: [PATCH] iio: humidity: hts221: fix division by zero in calibration data parsing

[Andy Shevchenko]

On Tue, Aug 25, 2026 at 05:21:10PM +0800, Yang Zi wrote:
> hts221_parse_temp_caldata() and hts221_parse_rh_caldata() compute the
> sensor slope as ((cal_y1 - cal_y0) * 8000) / (cal_x1 - cal_x0). If the
> device reports cal_x1 == cal_x0 the division causes a divide-by-zero
> error.
> 
> Return -EINVAL when cal_x1 == cal_x0 in both functions before performing
> the division.

Do you have HW to test? Any fault injection perhaps?
The problem with div-by-0 is that it's implementation defined, meaning
that it's how compiler decides. Now, the question is, what will compiler
do in the current code (no patch applied)?

...

>          return err;

>      cal_x1 = le16_to_cpu(val);

>  

I would remove this blank line as it's coupled with the above.

> +    if (cal_x1 == cal_x0)
> +        return -EINVAL;
> +

>      slope = &hw->sensors[HTS221_SENSOR_T].slope;
>      b_gen = &hw->sensors[HTS221_SENSOR_T].b_gen;

Ditto for the rest.


-- 
With Best Regards,
Andy Shevchenko