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Fri, 17 Jul 2026 13:59:44 -0700 (PDT) From: Luiz Angelo Daros de Luca Date: Fri, 17 Jul 2026 17:59:16 -0300 Subject: [PATCH v2 3/6] hwmon: (adt7470) Fix busy-loop and I2C flooding in update thread Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260717-adt7470_thermalzone-v2-3-a55147958fad@gmail.com> References: <20260717-adt7470_thermalzone-v2-0-a55147958fad@gmail.com> In-Reply-To: <20260717-adt7470_thermalzone-v2-0-a55147958fad@gmail.com> To: Guenter Roeck , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Chris Packham , Andrew Morton , "Darrick J. Wong" , =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= Cc: linux-hwmon@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Luiz Angelo Daros de Luca , linux-pwm@vger.kernel.org, sashiko-bot@kernel.org X-Mailer: b4 0.15.2 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 --- drivers/hwmon/adt7470.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/hwmon/adt7470.c b/drivers/hwmon/adt7470.c index 481d51617f4b..77e7be692790 100644 --- a/drivers/hwmon/adt7470.c +++ b/drivers/hwmon/adt7470.c @@ -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; -- 2.55.0