linux-hardening - Re: [PATCH] rtc: Move variable into switch case statement

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Date:   Mon, 13 Dec 2021 18:47:21 -0600
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        linux-kernel@...r.kernel.org, linux-rtc@...r.kernel.org,
        linux-hardening@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>
Subject: Re: [PATCH] rtc: Move variable into switch case statement

On Wed, Dec 08, 2021 at 08:39:15PM -0800, Kees Cook wrote:
> When building with automatic stack variable initialization, GCC 12
> complains about variables defined outside of switch case statements.
> Move the variable into the case that uses it, which silences the warning:
> 
> drivers/rtc/dev.c: In function 'rtc_dev_ioctl':
> drivers/rtc/dev.c:394:30: warning: statement will never be executed [-Wswitch-unreachable]
>   394 |                         long offset;
>       |                              ^~~~~~
> 
> Fixes: 6a8af1b6568a ("rtc: add parameter ioctl")
> Signed-off-by: Kees Cook <keescook@...omium.org>

Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Thanks
--
Gustavo

> ---
>  drivers/rtc/dev.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/rtc/dev.c b/drivers/rtc/dev.c
> index e104972a28fd..69325aeede1a 100644
> --- a/drivers/rtc/dev.c
> +++ b/drivers/rtc/dev.c
> @@ -391,14 +391,14 @@ static long rtc_dev_ioctl(struct file *file,
>  		}
>  
>  		switch(param.param) {
> -			long offset;
>  		case RTC_PARAM_FEATURES:
>  			if (param.index != 0)
>  				err = -EINVAL;
>  			param.uvalue = rtc->features[0];
>  			break;
>  
> -		case RTC_PARAM_CORRECTION:
> +		case RTC_PARAM_CORRECTION: {
> +			long offset;
>  			mutex_unlock(&rtc->ops_lock);
>  			if (param.index != 0)
>  				return -EINVAL;
> @@ -407,7 +407,7 @@ static long rtc_dev_ioctl(struct file *file,
>  			if (err == 0)
>  				param.svalue = offset;
>  			break;
> -
> +		}
>  		default:
>  			if (rtc->ops->param_get)
>  				err = rtc->ops->param_get(rtc->dev.parent, &param);
> -- 
> 2.30.2
> 
> 
> 
>