linux-kernel - Re: [PATCH] hwmon: applesmc: check status earlier.

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Date:   Fri, 21 Aug 2020 11:33:11 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     trix@...hat.com
Cc:     rydberg@...math.org, jdelvare@...e.com,
        linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] hwmon: applesmc: check status earlier.

On Thu, Aug 20, 2020 at 06:19:32AM -0700, trix@...hat.com wrote:
> From: Tom Rix <trix@...hat.com>
> 
> clang static analysis reports this representative problem
> 
> applesmc.c:758:10: warning: 1st function call argument is an
>   uninitialized value
>         left = be16_to_cpu(*(__be16 *)(buffer + 6)) >> 2;
>                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> buffer is filled by the earlier call
> 
> 	ret = applesmc_read_key(LIGHT_SENSOR_LEFT_KEY, ...
> 
> This problem is reported because a goto skips the status check.
> Other similar problems use data from applesmc_read_key before checking
> the status.  So move the checks to before the use.
> 
> Signed-off-by: Tom Rix <trix@...hat.com>

Applied.

Thanks,
Guenter

> ---
>  drivers/hwmon/applesmc.c | 31 ++++++++++++++++---------------
>  1 file changed, 16 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/hwmon/applesmc.c b/drivers/hwmon/applesmc.c
> index 316618409315..a18887990f4a 100644
> --- a/drivers/hwmon/applesmc.c
> +++ b/drivers/hwmon/applesmc.c
> @@ -753,15 +753,18 @@ static ssize_t applesmc_light_show(struct device *dev,
>  	}
>  
>  	ret = applesmc_read_key(LIGHT_SENSOR_LEFT_KEY, buffer, data_length);
> +	if (ret)
> +		goto out;
>  	/* newer macbooks report a single 10-bit bigendian value */
>  	if (data_length == 10) {
>  		left = be16_to_cpu(*(__be16 *)(buffer + 6)) >> 2;
>  		goto out;
>  	}
>  	left = buffer[2];
> +
> +	ret = applesmc_read_key(LIGHT_SENSOR_RIGHT_KEY, buffer, data_length);
>  	if (ret)
>  		goto out;
> -	ret = applesmc_read_key(LIGHT_SENSOR_RIGHT_KEY, buffer, data_length);
>  	right = buffer[2];
>  
>  out:
> @@ -810,12 +813,11 @@ static ssize_t applesmc_show_fan_speed(struct device *dev,
>  		  to_index(attr));
>  
>  	ret = applesmc_read_key(newkey, buffer, 2);
> -	speed = ((buffer[0] << 8 | buffer[1]) >> 2);
> -
>  	if (ret)
>  		return ret;
> -	else
> -		return snprintf(sysfsbuf, PAGE_SIZE, "%u\n", speed);
> +
> +	speed = ((buffer[0] << 8 | buffer[1]) >> 2);
> +	return snprintf(sysfsbuf, PAGE_SIZE, "%u\n", speed);
>  }
>  
>  static ssize_t applesmc_store_fan_speed(struct device *dev,
> @@ -851,12 +853,11 @@ static ssize_t applesmc_show_fan_manual(struct device *dev,
>  	u8 buffer[2];
>  
>  	ret = applesmc_read_key(FANS_MANUAL, buffer, 2);
> -	manual = ((buffer[0] << 8 | buffer[1]) >> to_index(attr)) & 0x01;
> -
>  	if (ret)
>  		return ret;
> -	else
> -		return snprintf(sysfsbuf, PAGE_SIZE, "%d\n", manual);
> +
> +	manual = ((buffer[0] << 8 | buffer[1]) >> to_index(attr)) & 0x01;
> +	return snprintf(sysfsbuf, PAGE_SIZE, "%d\n", manual);
>  }
>  
>  static ssize_t applesmc_store_fan_manual(struct device *dev,
> @@ -872,10 +873,11 @@ static ssize_t applesmc_store_fan_manual(struct device *dev,
>  		return -EINVAL;
>  
>  	ret = applesmc_read_key(FANS_MANUAL, buffer, 2);
> -	val = (buffer[0] << 8 | buffer[1]);
>  	if (ret)
>  		goto out;
>  
> +	val = (buffer[0] << 8 | buffer[1]);
> +
>  	if (input)
>  		val = val | (0x01 << to_index(attr));
>  	else
> @@ -951,13 +953,12 @@ static ssize_t applesmc_key_count_show(struct device *dev,
>  	u32 count;
>  
>  	ret = applesmc_read_key(KEY_COUNT_KEY, buffer, 4);
> -	count = ((u32)buffer[0]<<24) + ((u32)buffer[1]<<16) +
> -						((u32)buffer[2]<<8) + buffer[3];
> -
>  	if (ret)
>  		return ret;
> -	else
> -		return snprintf(sysfsbuf, PAGE_SIZE, "%d\n", count);
> +
> +	count = ((u32)buffer[0]<<24) + ((u32)buffer[1]<<16) +
> +						((u32)buffer[2]<<8) + buffer[3];
> +	return snprintf(sysfsbuf, PAGE_SIZE, "%d\n", count);
>  }
>  
>  static ssize_t applesmc_key_at_index_read_show(struct device *dev,