From 4faaa77d6b32347ea6af74d5fd2f34c3922aeee6 Mon Sep 17 00:00:00 2001 From: Gui-Dong Han Date: Tue, 25 Nov 2025 00:55:08 +0800 Subject: [PATCH] hwmon: (emc2103) Add locking to avoid TOCTOU The functions fan1_input_show and fan1_target_show check shared data for zero 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: Gui-Dong Han Link: https://lore.kernel.org/r/20251124165508.4667-1-hanguidong02@gmail.com Signed-off-by: Guenter Roeck --- drivers/hwmon/emc2103.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/hwmon/emc2103.c b/drivers/hwmon/emc2103.c index 60eddc7b02708..9b8e925af0300 100644 --- a/drivers/hwmon/emc2103.c +++ b/drivers/hwmon/emc2103.c @@ -277,8 +277,10 @@ fan1_input_show(struct device *dev, struct device_attribute *da, char *buf) { struct emc2103_data *data = emc2103_update_device(dev); int rpm = 0; + mutex_lock(&data->update_lock); if (data->fan_tach != 0) rpm = (FAN_RPM_FACTOR * data->fan_multiplier) / data->fan_tach; + mutex_unlock(&data->update_lock); return sprintf(buf, "%d\n", rpm); } @@ -363,10 +365,12 @@ fan1_target_show(struct device *dev, struct device_attribute *da, char *buf) struct emc2103_data *data = emc2103_update_device(dev); int rpm = 0; + mutex_lock(&data->update_lock); /* high byte of 0xff indicates disabled so return 0 */ if ((data->fan_target != 0) && ((data->fan_target & 0x1fe0) != 0x1fe0)) rpm = (FAN_RPM_FACTOR * data->fan_multiplier) / data->fan_target; + mutex_unlock(&data->update_lock); return sprintf(buf, "%d\n", rpm); } -- 2.47.3