linux-kernel - Re: [PATCH] ASoC: Intel: avs: Replace snprintf() with scnprintf()

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Message-ID: <aRSNrXnmPTElmx5H@kekkonen.localdomain>
Date: Wed, 12 Nov 2025 15:37:49 +0200
From: Sakari Ailus <sakari.ailus@...ux.intel.com>
To: hariconscious@...il.com
Cc: cezary.rojewski@...el.com, liam.r.girdwood@...ux.intel.com,
	peter.ujfalusi@...ux.intel.com, yung-chuan.liao@...ux.intel.com,
	ranjani.sridharan@...ux.intel.com, kai.vehmanen@...ux.intel.com,
	pierre-louis.bossart@...ux.dev, broonie@...nel.org, perex@...ex.cz,
	tiwai@...e.com, amadeuszx.slawinski@...ux.intel.com,
	khalid@...nel.org, shuah@...nel.org, david.hunter.linux@...il.com,
	linux-sound@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ASoC: Intel: avs: Replace snprintf() with scnprintf()

Hi HariKrishna,

On Wed, Nov 12, 2025 at 05:32:35PM +0530, hariconscious@...il.com wrote:
> From: HariKrishna Sagala <hariconscious@...il.com>
> 
> As per the C99 standard snprintf() returns the length of the data
> that *would have been* written if there were enough space for it.
> It's generally considered safer to use the scnprintf() variant.

Not only that, but the code assumes scnprintf() behaviour to function
correctly. This should be reflected in the commit message. I.e. this is a
bugfix and should probably be cc'd to stable. Could you provide a Fixes:
tag as well?

The change itself seems fine to me, apart from indentation.

> 
> Link: https://github.com/KSPP/linux/issues/105
> Signed-off-by: HariKrishna Sagala <hariconscious@...il.com>
> ---
> This patch replaces snprintf() varaint with scnprintf() in
> scenario to know the actual length of the data rather than *would
> have been* written data of snprintf().
> No functional changes intended.
> Reference Links:
> https://lwn.net/Articles/69419/
> https://www.kernel.org/doc/html/latest/core-api/kernel-api.html#c.snprintf
> 
> Note:
> Compile & boot tested with necessary config parameters.
> Other areas of AVS uses scnprintf() variant.
> 
>  sound/soc/intel/avs/debugfs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/sound/soc/intel/avs/debugfs.c b/sound/soc/intel/avs/debugfs.c
> index 3534de46f9e4..100b95bfcd78 100644
> --- a/sound/soc/intel/avs/debugfs.c
> +++ b/sound/soc/intel/avs/debugfs.c
> @@ -119,7 +119,7 @@ static ssize_t probe_points_read(struct file *file, char __user *to, size_t coun
>  	}
>  
>  	for (i = 0; i < num_desc; i++) {
> -		ret = snprintf(buf + len, PAGE_SIZE - len,
> +		ret = scnprintf(buf + len, PAGE_SIZE - len,
>  			       "Id: %#010x  Purpose: %d  Node id: %#x\n",
>  			       desc[i].id.value, desc[i].purpose, desc[i].node_id.val);
>  		if (ret < 0)
> 
> base-commit: 24172e0d79900908cf5ebf366600616d29c9b417

-- 
Kind regards,

Sakari Ailus