[PATCH 6.4 267/800] hwmon: (f71882fg) prevent possible division by zero

Greg Kroah-Hartman
2023-07-16T20:05:19Z

From: Nikita Zhandarovich <n.zhandarovich@fintech.ru>

[ Upstream commit 0babf89c9cca7e074d6e59893e462e4886f481cc ]

In the unlikely event that something goes wrong with the device and
its registers, the fan_from_reg() function may return 0. This value
will cause a division-by-zero error in the show_pwm() function.

To prevent this, test the value of
fan_from_reg(data->fan_full_speed[nr]) against 0 before performing
the division. If the division-by-zero error is avoided, assign 0 to
the val variable.

Found by Linux Verification Center (linuxtesting.org) with static
analysis tool SVACE.

Fixes: df9ec2dae094 ("hwmon: (f71882fg) Reorder symbols to get rid of a few forward declarations")
Signed-off-by: Nikita Zhandarovich <n.zhandarovich@fintech.ru>
Link: https://lore.kernel.org/r/20230510143537.145060-1-n.zhandarovich@fintech.ru
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/hwmon/f71882fg.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/hwmon/f71882fg.c b/drivers/hwmon/f71882fg.c
index 70121482a6173..27207ec6f7feb 100644
--- a/drivers/hwmon/f71882fg.c
+++ b/drivers/hwmon/f71882fg.c
@@ -1096,8 +1096,11 @@ static ssize_t show_pwm(struct device *dev,
val = data->pwm[nr];
else {
/* RPM mode */
- val = 255 * fan_from_reg(data->fan_target[nr])
- / fan_from_reg(data->fan_full_speed[nr]);
+ if (fan_from_reg(data->fan_full_speed[nr]))
+ val = 255 * fan_from_reg(data->fan_target[nr])
+ / fan_from_reg(data->fan_full_speed[nr]);
+ else
+ val = 0;
}
mutex_unlock(&data->update_lock);
return sprintf(buf, "%d\n", val);
--
2.39.2