From 5a15f8d87a007f69ff4178da3bad511c7bf8aefe Mon Sep 17 00:00:00 2001 From: Nikita Zhandarovich Date: Fri, 29 May 2026 17:18:36 +0300 Subject: [PATCH] hwmon: (it87) Clamp negative values to zero in set_fan() [ Upstream commit 7f8581c70a3bd50a932d3d2d253e99c5ec3eda74 ] set_fan() parses user input with kstrtol() and passes the resulting value to FAN16_TO_REG() on chips with 16-bit fan support. Negative fan speeds are not meaningful and should be rejected before conversion. Worst scenario, one may be able to abuse undefined behaviour of signed overflow to possibly induce rpm * 2 == 0 in FAN16_TO_REG(), thus causing a division by zero. Instead, clamp val < 0 to zero and keep the conversion in its valid input domain, avoiding unsafe arithmetic in the register conversion path. Found by Linux Verification Center (linuxtesting.org) with static analysis tool SVACE. Fixes: 17d648bf5786 ("it87: Add support for the IT8716F") Signed-off-by: Nikita Zhandarovich Link: https://lore.kernel.org/r/20260529141839.1639287-1-n.zhandarovich@fintech.ru Signed-off-by: Guenter Roeck Signed-off-by: Sasha Levin --- drivers/hwmon/it87.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/hwmon/it87.c b/drivers/hwmon/it87.c index 51882f7386cc..716afea0db24 100644 --- a/drivers/hwmon/it87.c +++ b/drivers/hwmon/it87.c @@ -1400,6 +1400,9 @@ static ssize_t set_fan(struct device *dev, struct device_attribute *attr, if (kstrtol(buf, 10, &val) < 0) return -EINVAL; + if (val < 0) + val = 0; + err = it87_lock(data); if (err) return err;