linux-kernel - [PATCH v5 1/2] hwmon: (lm90) Prevent integer underflows of temperature calculations

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Date:   Wed, 23 Jun 2021 07:22:30 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Zhang Rui <rui.zhang@...el.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Amit Kucheria <amitk@...nel.org>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>
Cc:     linux-hwmon@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org
Subject: [PATCH v5 1/2] hwmon: (lm90) Prevent integer underflows of temperature calculations

The min/max/crit and all other temperature values that are passed to
the driver are unlimited and value that is close to INT_MIN results in
integer underflow of the temperature calculations made by the driver
for LM99 sensor. Temperature hysteresis is among those values that need
to be limited, but limiting of hysteresis is independent from the sensor
version. Add the missing limits.

Signed-off-by: Dmitry Osipenko <digetx@...il.com>
---
 drivers/hwmon/lm90.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/hwmon/lm90.c b/drivers/hwmon/lm90.c
index b53f17511b05..567b7c521f38 100644
--- a/drivers/hwmon/lm90.c
+++ b/drivers/hwmon/lm90.c
@@ -1029,8 +1029,11 @@ static int lm90_set_temp11(struct lm90_data *data, int index, long val)
 	int err;
 
 	/* +16 degrees offset for temp2 for the LM99 */
-	if (data->kind == lm99 && index <= 2)
+	if (data->kind == lm99 && index <= 2) {
+		/* prevent integer underflow */
+		val = max(val, -128000l);
 		val -= 16000;
+	}
 
 	if (data->kind == adt7461 || data->kind == tmp451)
 		data->temp11[index] = temp_to_u16_adt7461(data, val);
@@ -1089,8 +1092,11 @@ static int lm90_set_temp8(struct lm90_data *data, int index, long val)
 	int err;
 
 	/* +16 degrees offset for temp2 for the LM99 */
-	if (data->kind == lm99 && index == 3)
+	if (data->kind == lm99 && index == 3) {
+		/* prevent integer underflow */
+		val = max(val, -128000l);
 		val -= 16000;
+	}
 
 	if (data->kind == adt7461 || data->kind == tmp451)
 		data->temp8[index] = temp_to_u8_adt7461(data, val);
@@ -1137,6 +1143,9 @@ static int lm90_set_temphyst(struct lm90_data *data, long val)
 	else
 		temp = temp_from_s8(data->temp8[LOCAL_CRIT]);
 
+	/* prevent integer underflow */
+	val = max(val, -128000l);
+
 	data->temp_hyst = hyst_to_reg(temp - val);
 	err = i2c_smbus_write_byte_data(client, LM90_REG_W_TCRIT_HYST,
 					data->temp_hyst);
-- 
2.30.2