Commit 07272e88 authored by Gui-Dong Han's avatar Gui-Dong Han Committed by Guenter Roeck
Browse files

hwmon: (w83l786ng) Convert macros to functions to avoid TOCTOU 

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: 85f03bcc ("hwmon: Add support for Winbond W83L786NG/NR")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarGui-Dong Han <hanguidong02@gmail.com>
Link: https://lore.kernel.org/r/20251128123816.3670-1-hanguidong02@gmail.com


Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
parent 02f0ad8e

drivers/hwmon/w83l786ng.c

+18 −8
Original line number Diff line number Diff line
@@ -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 *dev, struct device_attribute *attr, \ 
	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 device_attribute *attr, 


	/* 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 device_attribute *attr, char *buf) 
	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