Re: [PATCH v1] drivers/hwmon/adm9240: fix data race in adm9240_fan_read

[Guenter Roeck <linux@xxxxxxxxxxxx>]

On 9/22/22 16:33, Li Zhong wrote:
> In
> adm9240_read()
>    adm9240_fan_read()
>      adm9240_write_fan_div(),
>
> it assumes that the caller of adm9240_write_fan_div() must hold
> data->update_lock. Otherwise, it may cause data races when data is
> updated by other threads.
>
> Signed-off-by: Li Zhong <floridsleeves@xxxxxxxxx>
> ---
>   drivers/hwmon/adm9240.c | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/drivers/hwmon/adm9240.c b/drivers/hwmon/adm9240.c
> index 483cd757abd3..d93ae3147994 100644
> --- a/drivers/hwmon/adm9240.c
> +++ b/drivers/hwmon/adm9240.c
> @@ -501,6 +501,7 @@ static int adm9240_fan_read(struct device *dev, u32 attr, int channel, long *val
>   
>   	switch (attr) {
>   	case hwmon_fan_input:
> +		mutex_lock(&data->update_lock);
>   		err = regmap_read(data->regmap, ADM9240_REG_FAN(channel), &regval);
>   		if (err < 0)
>   			return err;
> @@ -511,6 +512,7 @@ static int adm9240_fan_read(struct device *dev, u32 attr, int channel, long *val
>   			if (err)
>   				return err;

The mutex also needs to be released here (in the error handling path).

>   		}
> +		mutex_unlock(&data->update_lock);
>   		*val = FAN_FROM_REG(regval, BIT(data->fan_div[channel]));
>   		break;
>   	case hwmon_fan_div: