Messages in this thread Patch in this message |  | | From | "Pradhan, Sanman" <> | | Subject | [PATCH v2 2/3] hwmon: (isl28022) Fix integer overflow in power calculation on 32-bit | | Date | Tue, 7 Apr 2026 17:38:01 +0000 |
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From: Sanman Pradhan <psanman@juniper.net>
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 intermediates with div_u64() and multiply before dividing to retain precision. Power is inherently non-negative, so unsigned types are the natural fit. Clamp the result to LONG_MAX before returning it through the hwmon callback, following the pattern used by ina238.
Fixes: 39671a14df4f2 ("hwmon: (isl28022) new driver for ISL28022 power monitor") Cc: stable@vger.kernel.org Signed-off-by: Sanman Pradhan <psanman@juniper.net> --- v2: - Switch from s64/div_s64() to u64/div_u64() since power is inherently non-negative, avoiding implicit u32-to-s32 narrowing of the shunt divisor
drivers/hwmon/isl28022.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/drivers/hwmon/isl28022.c b/drivers/hwmon/isl28022.c index c2e559dde63f..d233a7b3f327 100644 --- a/drivers/hwmon/isl28022.c +++ b/drivers/hwmon/isl28022.c @@ -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> @@ -178,6 +179,7 @@ static int isl28022_read_power(struct device *dev, u32 attr, long *val) struct isl28022_data *data = dev_get_drvdata(dev); unsigned int regval; int err; + u64 tmp; switch (attr) { case hwmon_power_input: @@ -185,8 +187,9 @@ static int isl28022_read_power(struct device *dev, u32 attr, long *val) ISL28022_REG_POWER, ®val); if (err < 0) return err; - *val = ((51200000L * ((long)data->gain)) / - (long)data->shunt) * (long)regval; + tmp = (u64)51200000 * data->gain * regval; + tmp = div_u64(tmp, data->shunt); + *val = clamp_val(tmp, 0, LONG_MAX); break; default: return -EOPNOTSUPP; -- 2.34.1
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