[RFC] hwmon: (nct6775-core) Fix overflows seen when writing limit attributes

[Pei Xiao <xiaopei01@xxxxxxxxxx>]

hi Guenter Roeck,
  Excuse me, may I ask a question?
  When I see this commit (Fixes: 0403e10bf082 ("hwmon: (nct6775-core) 
Fix underflows seen when writing limit attributes")), I found an issue,
DIV_ROUND_CLOSEST() after kstrtoul() results in an overflow if a large
number such as 18446744073709551615 is provided by the user.
Fix it by reordering clamp_val() and DIV_ROUND_CLOSEST() operations.

If the issue described above does indeed exist, I will send an formal patch.


diff --git a/drivers/hwmon/nct6775-core.c b/drivers/hwmon/nct6775-core.c
index 934fed3dd586..12ee2ca4a6d6 100644
--- a/drivers/hwmon/nct6775-core.c
+++ b/drivers/hwmon/nct6775-core.c
@@ -2878,8 +2878,7 @@ store_target_temp(struct device *dev, struct 
device_attribute *attr,
        if (err < 0)
                return err;

-       val = clamp_val(DIV_ROUND_CLOSEST(val, 1000), 0,
-                       data->target_temp_mask);
+       val = DIV_ROUND_CLOSEST(clamp_val(val, 0, data->tolerance_mask * 
1000), 1000);

        mutex_lock(&data->update_lock);
        data->target_temp[nr] = val;
@@ -2959,7 +2958,7 @@ store_temp_tolerance(struct device *dev, struct 
device_attribute *attr,
                return err;

        /* Limit tolerance as needed */
-       val = clamp_val(DIV_ROUND_CLOSEST(val, 1000), 0, 
data->tolerance_mask);
+       val = DIV_ROUND_CLOSEST(clamp_val(val, 0, data->tolerance_mask * 
1000), 1000);

        mutex_lock(&data->update_lock);
        data->temp_tolerance[index][nr] = val;
@@ -3085,7 +3084,7 @@ store_weight_temp(struct device *dev, struct 
device_attribute *attr,
        if (err < 0)
                return err;

-       val = clamp_val(DIV_ROUND_CLOSEST(val, 1000), 0, 255);
+       val = DIV_ROUND_CLOSEST(clamp_val(val, 0, 25500), 1000);

        mutex_lock(&data->update_lock);
        data->weight_temp[index][nr] = val;

Thanks!