From: Axel Lin <axel.lin@ingics.com>
Date: Thu, 31 Jul 2014 01:43:19 +0000 (+0800)
Subject: hwmon: (amc6821) Fix possible race condition bug
X-Git-Tag: v4.14-rc1~7102^2~84
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=cf44819c98db11163f58f08b822d626c7a8f5188;p=platform%2Fkernel%2Flinux-rpi.git

hwmon: (amc6821) Fix possible race condition bug

Ensure mutex lock protects the read-modify-write period to prevent possible
race condition bug.
In additional, update data->valid should also be protected by the mutex lock.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Cc: stable@vger.kernel.org
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---

diff --git a/drivers/hwmon/amc6821.c b/drivers/hwmon/amc6821.c
index 9f2be3d..8a67ec6 100644
--- a/drivers/hwmon/amc6821.c
+++ b/drivers/hwmon/amc6821.c
@@ -360,11 +360,13 @@ static ssize_t set_pwm1_enable(
 	if (config)
 		return config;
 
+	mutex_lock(&data->update_lock);
 	config = i2c_smbus_read_byte_data(client, AMC6821_REG_CONF1);
 	if (config < 0) {
 			dev_err(&client->dev,
 			"Error reading configuration register, aborting.\n");
-			return config;
+			count = config;
+			goto unlock;
 	}
 
 	switch (val) {
@@ -381,14 +383,15 @@ static ssize_t set_pwm1_enable(
 		config |= AMC6821_CONF1_FDRC1;
 		break;
 	default:
-		return -EINVAL;
+		count = -EINVAL;
+		goto unlock;
 	}
-	mutex_lock(&data->update_lock);
 	if (i2c_smbus_write_byte_data(client, AMC6821_REG_CONF1, config)) {
 			dev_err(&client->dev,
 			"Configuration register write error, aborting.\n");
 			count = -EIO;
 	}
+unlock:
 	mutex_unlock(&data->update_lock);
 	return count;
 }
@@ -493,8 +496,9 @@ static ssize_t set_temp_auto_point_temp(
 		return -EINVAL;
 	}
 
-	data->valid = 0;
 	mutex_lock(&data->update_lock);
+	data->valid = 0;
+
 	switch (ix) {
 	case 0:
 		ptemp[0] = clamp_val(val / 1000, 0,
@@ -658,13 +662,14 @@ static ssize_t set_fan1_div(
 	if (config)
 		return config;
 
+	mutex_lock(&data->update_lock);
 	config = i2c_smbus_read_byte_data(client, AMC6821_REG_CONF4);
 	if (config < 0) {
 		dev_err(&client->dev,
 			"Error reading configuration register, aborting.\n");
-		return config;
+		count = config;
+		goto EXIT;
 	}
-	mutex_lock(&data->update_lock);
 	switch (val) {
 	case 2:
 		config &= ~AMC6821_CONF4_PSPR;