linux-kernel - Re: [PATCH] ALSA: hda - Fix and neaten print_nid_path/debug

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Date:	Mon, 07 Jul 2014 09:35:07 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Joe Perches <joe@...ches.com>
Cc:	alsa-devel@...a-project.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ALSA: hda - Fix and neaten print_nid_path/debug_badness

At Sat, 05 Jul 2014 13:02:02 -0700,
Joe Perches wrote:
> 
> print_nid_path has a possible buffer overflow if
> struct nid_path.path values are > 256.
> 
> Avoid this and neaten the output to remove the leading ':'
> 
> Neaten debug_badness to always verify arguments.
> 
> Signed-off-by: Joe Perches <joe@...ches.com>

Thanks, applied.

Although the overflow would never happen in practice (the id can't be
over 8 bit from the definition in the HD-audio controller side), it's
still better to have a proper check.


Takashi

> ---
>  sound/pci/hda/hda_generic.c | 20 +++++++++++---------
>  1 file changed, 11 insertions(+), 9 deletions(-)
> 
> diff --git a/sound/pci/hda/hda_generic.c b/sound/pci/hda/hda_generic.c
> index 589e47c..b293583 100644
> --- a/sound/pci/hda/hda_generic.c
> +++ b/sound/pci/hda/hda_generic.c
> @@ -350,16 +350,16 @@ static void print_nid_path(struct hda_codec *codec,
>  			   const char *pfx, struct nid_path *path)
>  {
>  	char buf[40];
> +	char *pos = buf;
>  	int i;
>  
> +	*pos = 0;
> +	for (i = 0; i < path->depth; i++)
> +		pos += scnprintf(pos, sizeof(buf) - (pos - buf), "%s%02x",
> +				 pos != buf ? ":" : "",
> +				 path->path[i]);
>  
> -	buf[0] = 0;
> -	for (i = 0; i < path->depth; i++) {
> -		char tmp[4];
> -		sprintf(tmp, ":%02x", path->path[i]);
> -		strlcat(buf, tmp, sizeof(buf));
> -	}
> -	codec_dbg(codec, "%s path: depth=%d %s\n", pfx, path->depth, buf);
> +	codec_dbg(codec, "%s path: depth=%d '%s'\n", pfx, path->depth, buf);
>  }
>  
>  /* called recursively */
> @@ -1700,9 +1700,11 @@ static int fill_and_eval_dacs(struct hda_codec *codec,
>  #define DEBUG_BADNESS
>  
>  #ifdef DEBUG_BADNESS
> -#define debug_badness(fmt, args...)	codec_dbg(codec, fmt, ##args)
> +#define debug_badness(fmt, ...)						\
> +	codec_dbg(codec, fmt, ##__VA_ARGS__)
>  #else
> -#define debug_badness(...)
> +#define debug_badness(fmt, ...)						\
> +	do { if (0) codec_dbg(codec, fmt, ##__VA_ARGS__); } while (0)
>  #endif
>  
>  #ifdef DEBUG_BADNESS
> 
> 
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