linux-kernel - Re: [PATCH] iio: addac: ad74115: Fix use of uninitialized variable rate

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Message-ID: <1254dfd7-e872-4c65-bd17-8015e1b2eba4@baylibre.com>
Date: Thu, 10 Apr 2025 09:51:57 -0500
From: David Lechner <dlechner@...libre.com>
To: Purva Yeshi <purvayeshi550@...il.com>, cosmin.tanislav@...log.com,
 lars@...afoo.de, Michael.Hennerich@...log.com, jic23@...nel.org
Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: addac: ad74115: Fix use of uninitialized variable
 rate

On 4/9/25 3:29 PM, Purva Yeshi wrote:
> Fix Smatch-detected error:
> drivers/iio/addac/ad74115.c:823 _ad74115_get_adc_code() error:
> uninitialized symbol 'rate'.
> 
> The variable rate was declared but not given any value before being used
> in a division. If the code reached that point without setting rate, it
> would cause unpredictable behavior.
> 
> Declare and initialize 'rate' to zero inside the 'else' block where it is
> used. This ensures 'rate' is always initialized before being passed to
> DIV_ROUND_CLOSEST.
> 
> Signed-off-by: Purva Yeshi <purvayeshi550@...il.com>
> ---
>  drivers/iio/addac/ad74115.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/addac/ad74115.c b/drivers/iio/addac/ad74115.c
> index a7e480f2472d..26770c68e5fa 100644
> --- a/drivers/iio/addac/ad74115.c
> +++ b/drivers/iio/addac/ad74115.c
> @@ -814,7 +814,7 @@ static int _ad74115_get_adc_code(struct ad74115_state *st,
>  			return -ETIMEDOUT;
>  	} else {
>  		unsigned int regval, wait_time;
> -		int rate;
> +		int rate = 0;
>  
>  		ret = ad74115_get_adc_rate(st, channel, &rate);
>  		if (ret < 0)

I don't see how rate could be used uninitialized since we are
returning the error if ad74115_get_adc_rate() fails.

Also, initializing to 0 would then cause a divide by 0 error
if that value was actually used later in the code.