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>

1 files changed, 11 insertions, 6 deletions

diff --git a/drivers/hwmon/amc6821.c b/drivers/hwmon/amc6821.c
index 9f2be3dd28f3..8a67ec6279a4 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;