[PATCH 6.12 289/567] hwmon: (w83l786ng) Convert macros to functions to avoid TOCTOU

Greg Kroah-Hartman
2026-01-06T17:30:08Z

From: Gui-Dong Han <hanguidong02@gmail.com>

commit 07272e883fc61574b8367d44de48917f622cdd83 upstream.

The macros FAN_FROM_REG and TEMP_FROM_REG evaluate their arguments
multiple times. When used in lockless contexts involving shared driver
data, this causes Time-of-Check to Time-of-Use (TOCTOU) race
conditions.

Convert the macros to static functions. This guarantees that arguments
are evaluated only once (pass-by-value), preventing the race
conditions.

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: 85f03bccd6e0 ("hwmon: Add support for Winbond W83L786NG/NR")
Cc: stable@vger.kernel.org
Signed-off-by: Gui-Dong Han <hanguidong02@gmail.com>
Link: https://lore.kernel.org/r/20251128123816.3670-1-hanguidong02@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/hwmon/w83l786ng.c | 26 ++++++++++++++++++--------
1 file changed, 18 insertions(+), 8 deletions(-)

--- a/drivers/hwmon/w83l786ng.c
+++ b/drivers/hwmon/w83l786ng.c
@@ -76,15 +76,25 @@ 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 temp */
#define TEMP_TO_REG(val) (clamp_val(((val) < 0 ? (val) + 0x100 * 1000 \
: (val)) / 1000, 0, 0xff))
-#define TEMP_FROM_REG(val) (((val) & 0x80 ? \
- (val) - 0x100 : (val)) * 1000)
+
+static int temp_from_reg(int val)
+{
+ if (val & 0x80)
+ return (val - 0x100) * 1000;
+ return val * 1000;
+}

/*
* The analog voltage inputs have 8mV LSB. Since the sysfs output is
@@ -280,7 +290,7 @@ static ssize_t show_##reg(struct device
int nr = to_sensor_dev_attr(attr)->index; \
struct w83l786ng_data *data = w83l786ng_update_device(dev); \
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);
@@ -347,7 +357,7 @@ store_fan_div(struct device *dev, struct

/* Save fan_min */
mutex_lock(&data->update_lock);
- 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]));

data->fan_div[nr] = DIV_TO_REG(val);

@@ -409,7 +419,7 @@ show_temp(struct device *dev, struct dev
int nr = sensor_attr->nr;
int index = sensor_attr->index;
struct w83l786ng_data *data = w83l786ng_update_device(dev);
- return sprintf(buf, "%d\n", TEMP_FROM_REG(data->temp[nr][index]));
+ return sprintf(buf, "%d\n", temp_from_reg(data->temp[nr][index]));
}

static ssize_t