[PATCH 3.13 123/187] hwmon: (amc6821) Fix possible race condition bug

Kamal Mostafa
2014-09-15T22:19:56Z

From: Axel Lin <axel.lin@ingics.com>

commit cf44819c98db11163f58f08b822d626c7a8f5188 upstream.

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>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
drivers/hwmon/amc6821.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)

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;
--
1.9.1