linux-kernel - [PATCH v2] hwmon: (lm80) fix a missing check of the status of SMBus read

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Date:   Fri, 21 Dec 2018 13:01:33 -0600
From:   Kangjie Lu <kjlu@....edu>
To:     kjlu@....edu
Cc:     pakki001@....edu, Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] hwmon: (lm80) fix a missing check of the status of SMBus read

If lm80_read_value() fails, it returns a negative number instead of the
correct read data. Therefore, we should avoid using the data if it
fails.

The fix checks if lm80_read_value() fails, and if so, returns with the
error number.

Signed-off-by: Kangjie Lu <kjlu@....edu>
---
 drivers/hwmon/lm80.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/hwmon/lm80.c b/drivers/hwmon/lm80.c
index 08e3945a6fbf..d91333557f04 100644
--- a/drivers/hwmon/lm80.c
+++ b/drivers/hwmon/lm80.c
@@ -360,6 +360,7 @@ static ssize_t set_fan_div(struct device *dev, struct device_attribute *attr,
 	struct i2c_client *client = data->client;
 	unsigned long min, val;
 	u8 reg;
+	int rv;
 	int err = kstrtoul(buf, 10, &val);
 	if (err < 0)
 		return err;
@@ -390,8 +391,11 @@ static ssize_t set_fan_div(struct device *dev, struct device_attribute *attr,
 		return -EINVAL;
 	}
 
-	reg = (lm80_read_value(client, LM80_REG_FANDIV) &
-	       ~(3 << (2 * (nr + 1)))) | (data->fan_div[nr] << (2 * (nr + 1)));
+	rv = lm80_read_value(client, LM80_REG_FANDIV);
+	if (rv < 0)
+		return rv;
+	reg = (rv & ~(3 << (2 * (nr + 1))))
+	    | (data->fan_div[nr] << (2 * (nr + 1)));
 	lm80_write_value(client, LM80_REG_FANDIV, reg);
 
 	/* Restore fan_min */
-- 
2.17.1