Commit 9eb4fb93 authored by Gui-Dong Han's avatar Gui-Dong Han Committed by Guenter Roeck
Browse files

hwmon: (adm1029) Add locking to avoid TOCTOU 

The function fan_show checks shared data for zero or invalid values
before using it as a divisor. These accesses are currently lockless. If
the data changes to zero between the check and the division, it causes a
divide-by-zero error.

Explicitly acquire the update lock around these checks and calculations
to ensure the data remains stable, preventing Time-of-Check to
Time-of-Use (TOCTOU) race conditions.

Link: https://lore.kernel.org/all/CALbr=LYJ_ehtp53HXEVkSpYoub+XYSTU8Rg=o1xxMJ8=5z8B-g@mail.gmail.com/


Signed-off-by: default avatarGui-Dong Han <hanguidong02@gmail.com>
Link: https://lore.kernel.org/r/20251126114047.10039-1-hanguidong02@gmail.com


Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
parent be89cf78

drivers/hwmon/adm1029.c

+3 −0
Original line number Diff line number Diff line
@@ -171,14 +171,17 @@ fan_show(struct device *dev, struct device_attribute *devattr, char *buf) 
	struct adm1029_data *data = adm1029_update_device(dev);

	u16 val;



	mutex_lock(&data->update_lock);

	if (data->fan[attr->index] == 0 ||

	    (data->fan_div[attr->index] & 0xC0) == 0 ||

	    data->fan[attr->index] == 255) {

		mutex_unlock(&data->update_lock);

		return sprintf(buf, "0\n");

	}



	val = 1880 * 120 / DIV_FROM_REG(data->fan_div[attr->index])

	    / data->fan[attr->index];

	mutex_unlock(&data->update_lock);

	return sprintf(buf, "%d\n", val);

}