diff options
| author | Gui-Dong Han <hanguidong02@gmail.com> | 2025-12-03 02:01:05 +0800 |
|---|---|---|
| committer | Guenter Roeck <linux@roeck-us.net> | 2025-12-07 14:10:18 -0800 |
| commit | 670d7ef945d3a84683594429aea6ab2cdfa5ceb4 (patch) | |
| tree | 6bbe82dc9f4f7209efe65ede4a294471b37a1b0d | |
| parent | 67a454e6b1c604555c04501c77b7fedc5d98a779 (diff) | |
| download | linux-670d7ef945d3a84683594429aea6ab2cdfa5ceb4.tar.gz | |
hwmon: (w83791d) Convert macros to functions to avoid TOCTOU
The macro FAN_FROM_REG evaluates its arguments multiple times. When used
in lockless contexts involving shared driver data, this leads to
Time-of-Check to Time-of-Use (TOCTOU) race conditions, potentially
causing divide-by-zero errors.
Convert the macro to a static function. This guarantees that arguments
are evaluated only once (pass-by-value), preventing the race
conditions.
Additionally, in store_fan_div, move the calculation of the minimum
limit inside the update lock. This ensures that the read-modify-write
sequence operates on consistent data.
Adhere to the principle of minimal changes by only converting macros
that evaluate arguments multiple times and are used in lockless
contexts.
Link: https://lore.kernel.org/all/CALbr=LYJ_ehtp53HXEVkSpYoub+XYSTU8Rg=o1xxMJ8=5z8B-g@mail.gmail.com/
Fixes: 9873964d6eb2 ("[PATCH] HWMON: w83791d: New hardware monitoring driver for the Winbond W83791D")
Cc: stable@vger.kernel.org
Signed-off-by: Gui-Dong Han <hanguidong02@gmail.com>
Link: https://lore.kernel.org/r/20251202180105.12842-1-hanguidong02@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
| -rw-r--r-- | drivers/hwmon/w83791d.c | 17 |
1 files changed, 11 insertions, 6 deletions
diff --git a/drivers/hwmon/w83791d.c b/drivers/hwmon/w83791d.c index ace854b370a054..996e36951f9dad 100644 --- a/drivers/hwmon/w83791d.c +++ b/drivers/hwmon/w83791d.c @@ -218,9 +218,14 @@ static u8 fan_to_reg(long rpm, int div) return clamp_val((1350000 + rpm * div / 2) / (rpm * div), 1, 254); } -#define FAN_FROM_REG(val, div) ((val) == 0 ? -1 : \ - ((val) == 255 ? 0 : \ - 1350000 / ((val) * (div)))) +static int fan_from_reg(int val, int div) +{ + if (val == 0) + return -1; + if (val == 255) + return 0; + return 1350000 / (val * div); +} /* for temp1 which is 8-bit resolution, LSB = 1 degree Celsius */ #define TEMP1_FROM_REG(val) ((val) * 1000) @@ -521,7 +526,7 @@ static ssize_t show_##reg(struct device *dev, struct device_attribute *attr, \ struct w83791d_data *data = w83791d_update_device(dev); \ int nr = sensor_attr->index; \ return sprintf(buf, "%d\n", \ - FAN_FROM_REG(data->reg[nr], DIV_FROM_REG(data->fan_div[nr]))); \ + fan_from_reg(data->reg[nr], DIV_FROM_REG(data->fan_div[nr]))); \ } show_fan_reg(fan); @@ -585,10 +590,10 @@ static ssize_t store_fan_div(struct device *dev, struct device_attribute *attr, if (err) return err; + mutex_lock(&data->update_lock); /* Save fan_min */ - min = FAN_FROM_REG(data->fan_min[nr], DIV_FROM_REG(data->fan_div[nr])); + min = fan_from_reg(data->fan_min[nr], DIV_FROM_REG(data->fan_div[nr])); - mutex_lock(&data->update_lock); data->fan_div[nr] = div_to_reg(nr, val); switch (nr) { |