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 9f2be3dd28f3007c557afd4683d053d8ff44a031..8a67ec6279a41d8da77fb0d643e242a6eeb4206b 100644 (file)
--- 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;