linux-kernel - Re: [PATCH] cpufreq: sun50i: Fix build warning around snprint()

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Date: Mon, 22 Apr 2024 23:39:58 +0100
From: Andre Przywara <andre.przywara@....com>
To: Viresh Kumar <viresh.kumar@...aro.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Yangtao Li
 <tiny.windzz@...il.com>, Chen-Yu Tsai <wens@...e.org>, Jernej Skrabec
 <jernej.skrabec@...il.com>, Samuel Holland <samuel@...lland.org>,
 linux-pm@...r.kernel.org, Vincent Guittot <vincent.guittot@...aro.org>,
 kernel test robot <lkp@...el.com>, linux-arm-kernel@...ts.infradead.org,
 linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpufreq: sun50i: Fix build warning around snprint()

On Mon, 22 Apr 2024 09:01:09 +0530
Viresh Kumar <viresh.kumar@...aro.org> wrote:

Hi,

> The Sun50i driver generates a warning with W=1:
> 
> warning: '%d' directive output may be truncated writing between 1 and 10 bytes into a region of size 2 [-Wformat-truncation=]
> 
> Fix it by allocating a big enough array to print an integer.
> 
> Reported-by: kernel test robot <lkp@...el.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202404191715.LDwMm2gP-lkp@intel.com/
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>

For the records: as it stands right now, "speed" will always be smaller
than 10 at the moment, but it's indeed better to play safe here.
So the fix makes sense to me and fixes the issue:

Reviewed-by: Andre Przywara <andre.przywara@....com>
Tested-by: Andre Przywara <andre.przywara@....com>

Cheers,
Andre

> ---
>  drivers/cpufreq/sun50i-cpufreq-nvmem.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/cpufreq/sun50i-cpufreq-nvmem.c b/drivers/cpufreq/sun50i-cpufreq-nvmem.c
> index 30e5c337611c..cd50cea16a87 100644
> --- a/drivers/cpufreq/sun50i-cpufreq-nvmem.c
> +++ b/drivers/cpufreq/sun50i-cpufreq-nvmem.c
> @@ -19,8 +19,6 @@
>  #include <linux/pm_opp.h>
>  #include <linux/slab.h>
>  
> -#define MAX_NAME_LEN	7
> -
>  #define NVMEM_MASK	0x7
>  #define NVMEM_SHIFT	5
>  
> @@ -208,7 +206,7 @@ static int sun50i_cpufreq_get_efuse(void)
>  static int sun50i_cpufreq_nvmem_probe(struct platform_device *pdev)
>  {
>  	int *opp_tokens;
> -	char name[MAX_NAME_LEN];
> +	char name[] = "speedXXXXXXXXXXX"; /* Integers can take 11 chars max */
>  	unsigned int cpu, supported_hw;
>  	struct dev_pm_opp_config config = {};
>  	int speed;
> @@ -235,7 +233,7 @@ static int sun50i_cpufreq_nvmem_probe(struct platform_device *pdev)
>  		config.supported_hw_count = 1;
>  	}
>  
> -	snprintf(name, MAX_NAME_LEN, "speed%d", speed);
> +	snprintf(name, sizeof(name), "speed%d", speed);
>  	config.prop_name = name;
>  
>  	for_each_possible_cpu(cpu) {