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hwmon: (adt7470) Fix busy-loop and I2C flooding in update thread

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When userspace configures 'auto_update_interval' to 0 via sysfs, the
background kthread executes schedule_timeout_interruptible(0), which
returns immediately.

If 'num_temp_sensors' is concurrently or previously set to 0, the
msleep_interruptible() delay inside adt7470_read_temperatures() also
becomes 0. This combination forces the background thread into a tight,
unbounded busy-loop, hogging the CPU and flooding the I2C bus with a
continuous stream of transactions.

Fix this vulnerability by raising the lower limit of the clamp_val in
auto_update_interval_store() from 0 to 500 milliseconds. This guarantees
a reasonable minimum sleep window between sensor updates, protecting the
system from intentional or accidental I2C bus denial of service.

Reported-by: sashiko-bot@kernel.org
Closes: https://lore.kernel.org/r/20260716213252.EACA71F000E9@smtp.kernel.org
Fixes: 89fac11cb3 ("adt7470: make automatic fan control really work")
Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
Link: https://lore.kernel.org/r/20260727-adt7470_fixes-v2-3-598e38a46ba6@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Luiz Angelo Daros de Luca 2026-07-27 21:22:19 -03:00 committed by Guenter Roeck
parent 05270bd38d
commit cb0b7f9c43
1 changed files with 1 additions and 1 deletions
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2
drivers/hwmon/adt7470.c
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@ -509,7 +509,7 @@ static ssize_t auto_update_interval_store(struct device *dev,
if (kstrtol(buf, 10, &temp))
return -EINVAL;
temp = clamp_val(temp, 0, 60000);
temp = clamp_val(temp, 500, 60000);
mutex_lock(&data->lock);
data->auto_update_interval = temp;