On Mon, Dec 19, 2022 at 07:04:57PM -0500, Cormier, Jonathan wrote:
> From: John Pruitt <jpruitt@xxxxxxxxxxxxxxxx>
>
> Use 64-bit values for intermediate calculations. Check for
> overflows and return INT_MAX if overflows happened.
>
> Signed-off-by: John Pruitt <jpruitt@xxxxxxxxxxxxxxxx>
> Signed-off-by: "Cormier, Jonathan" <jcormier@xxxxxxxxxxxxxxxx>
The problems here are introduced with the previous patch
and thus would need a Fixes: tag. It just doesn't make sense
to submit that as separate patch.
> ---
> drivers/hwmon/ltc2945.c | 20 +++++++++++++++-----
> 1 file changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/hwmon/ltc2945.c b/drivers/hwmon/ltc2945.c
> index fc7d399b2c85..7239422fc6db 100644
> --- a/drivers/hwmon/ltc2945.c
> +++ b/drivers/hwmon/ltc2945.c
> @@ -126,6 +126,10 @@ static long long ltc2945_reg_to_val(struct device *dev, u8 reg)
> }
> val *= 1000;
> val = DIV_ROUND_CLOSEST_ULL(val, shunt_resistor);
> + /* check for overflow, use MAX value if it happened */
> + if (val > INT_MAX)
> + val = INT_MAX;
> +
ltc2945_reg_to_val returns long long, and the calling code expects long long.
How would this ever overflow ?
> break;
> case LTC2945_VIN_H:
> case LTC2945_MAX_VIN_H:
> @@ -159,12 +163,14 @@ static long long ltc2945_reg_to_val(struct device *dev, u8 reg)
> }
>
> static int ltc2945_val_to_reg(struct device *dev, u8 reg,
> - unsigned long val)
> + unsigned long val_32)
> {
> struct ltc2945_data *data = dev_get_drvdata(dev);
> struct regmap *regmap = data->regmap;
> u32 shunt_resistor = data->shunt_resistor;
> unsigned int control;
> + /* use 64-bit val for intermediate calculations */
> + unsigned long long val = val_32;
This is unnnecessary. The parameter can be unsigned long long,
making the conversion automatic.
> int ret;
>
> switch (reg) {
> @@ -184,7 +190,7 @@ static int ltc2945_val_to_reg(struct device *dev, u8 reg,
> if (control & CONTROL_MULT_SELECT) {
> /* 25 mV * 25 uV = 0.625 uV resolution. */
> val *= shunt_resistor;
> - val = DIV_ROUND_CLOSEST(val, 625 * 1000);
> + val = DIV_ROUND_CLOSEST_ULL(val, 625LL * 1000LL);
> } else {
> /*
> * 0.5 mV * 25 uV = 0.0125 uV resolution.
> @@ -192,7 +198,7 @@ static int ltc2945_val_to_reg(struct device *dev, u8 reg,
> * accept loss of accuracy.
> */
> val *= shunt_resistor;
> - val = DIV_ROUND_CLOSEST(val, 25 * 1000) * 2;
> + val = DIV_ROUND_CLOSEST_ULL(val, 25LL * 1000LL) * 2;
> }
> break;
> case LTC2945_VIN_H:
> @@ -201,7 +207,7 @@ static int ltc2945_val_to_reg(struct device *dev, u8 reg,
> case LTC2945_MAX_VIN_THRES_H:
> case LTC2945_MIN_VIN_THRES_H:
> /* 25 mV resolution. */
> - val /= 25;
> + val = DIV_ROUND_CLOSEST_ULL(val, 25LL);
Unrelated change causing behavioral change. Not that I mind, but it is
still unrelated and would have to be a separate patch.
> break;
> case LTC2945_ADIN_H:
> case LTC2945_MAX_ADIN_H:
> @@ -218,11 +224,15 @@ static int ltc2945_val_to_reg(struct device *dev, u8 reg,
> case LTC2945_MIN_SENSE_THRES_H:
> /* 25 uV resolution. Convert to mA. */
> val *= shunt_resistor;
> - val = DIV_ROUND_CLOSEST(val, 25 * 1000);
> + val = DIV_ROUND_CLOSEST_ULL(val, 25LL * 1000LL);
> break;
> default:
> return -EINVAL;
> }
> + /* If val is too large, just return the max value */
> + if (val > INT_MAX)
> + return INT_MAX;
> +
While the return value is declared as int, the calling code expects
unsigned long. It would be better to adjust the return value and clamp
against ULONG_MAX.
> return val;
> }
>
> --
> 2.25.1
