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hwmon: (isl28022) Fix integer overflow in power calculation on 32-bit

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isl28022_read_power() computes:

  *val = ((51200000L * ((long)data->gain)) /
          (long)data->shunt) * (long)regval;

On 32-bit platforms, 'long' is 32 bits. With gain=8 and shunt=10000
(the default configuration):

  (51200000 * 8) / 10000 = 40960
  40960 * 65535 = 2,684,313,600

This exceeds LONG_MAX (2,147,483,647), resulting in signed integer
overflow.

Additionally, dividing before multiplying by regval loses precision
unnecessarily.

Use u64 arithmetic with div_u64() and multiply before dividing to
retain precision. The intermediate product cannot overflow u64
(worst case: 51200000 * 8 * 65535 = 26843136000000). Power is
inherently non-negative, so unsigned types are the natural fit.
Cap the result to LONG_MAX before returning it through the hwmon
callback.

Fixes: 39671a14df ("hwmon: (isl28022) new driver for ISL28022 power monitor")
Cc: stable@vger.kernel.org
Signed-off-by: Sanman Pradhan <psanman@juniper.net>
Link: https://lore.kernel.org/r/20260410002613.424557-1-sanman.pradhan@hpe.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Sanman Pradhan 2026-04-10 00:26:19 +00:00 committed by Guenter Roeck
parent 24c73e93d6
commit a7c0aaa50e
1 changed files with 3 additions and 2 deletions
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5
drivers/hwmon/isl28022.c
View File

@ -9,6 +9,7 @@
#include <linux/err.h>
#include <linux/hwmon.h>
#include <linux/i2c.h>
#include <linux/math64.h>
#include <linux/module.h>
#include <linux/regmap.h>
@ -185,8 +186,8 @@ static int isl28022_read_power(struct device *dev, u32 attr, long *val)
ISL28022_REG_POWER, &regval);
if (err < 0)
return err;
*val = ((51200000L * ((long)data->gain)) /
(long)data->shunt) * (long)regval;
*val = min(div_u64(51200000ULL * data->gain * regval,
data->shunt), LONG_MAX);
break;
default:
return -EOPNOTSUPP;