Re: [hwmon PATCH v2 3/8] hwmon: (adt7470) Fix busy-loop and I2C flooding in update thread

[Guenter Roeck <linux@roeck-us.net>]

On Mon, Jul 27, 2026 at 09:22:19PM -0300, Luiz Angelo Daros de Luca wrote:
> 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: 89fac11cb3e7 ("adt7470: make automatic fan control really work")
> Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>

Applied.

Thanks,
Guenter