linux-kernel - Re: [PATCH 9/9] sound/soc/codecs: Correct code taking the size of a pointer

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Date:	Sun, 13 Dec 2009 15:09:16 +0100
From:	walter harms <wharms@....de>
To:	Julia Lawall <julia@...u.dk>
Cc:	Liam Girdwood <lrg@...mlogic.co.uk>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.de>,
	alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 9/9] sound/soc/codecs: Correct code taking the size of
 a pointer



Julia Lawall schrieb:
> From: Julia Lawall <julia@...u.dk>
> 
> sizeof(codec->reg_cache) is just the size of the pointer.  Elsewhere in the
> file, codec->reg_cache is used with sizeof(wm8900_reg_defaults), so the
> code is changed to do the same here.
> 
> A simplified version of the semantic patch that finds this problem is as
> follows: (http://coccinelle.lip6.fr/)
> 
> // <smpl>
> @@
> expression *x;
> expression f;
> type T;
> @@
> 
> *f(...,(T)x,...)
> // </smpl>
> 
> Signed-off-by: Julia Lawall <julia@...u.dk>
> 
> ---
>  sound/soc/codecs/wm8900.c           |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/sound/soc/codecs/wm8900.c b/sound/soc/codecs/wm8900.c
> index c9438dd..dbc368c 100644
> --- a/sound/soc/codecs/wm8900.c
> +++ b/sound/soc/codecs/wm8900.c
> @@ -199,7 +199,7 @@ static void wm8900_reset(struct snd_soc_codec *codec)
>  	snd_soc_write(codec, WM8900_REG_RESET, 0);
>  
>  	memcpy(codec->reg_cache, wm8900_reg_defaults,
> -	       sizeof(codec->reg_cache));
> +	       sizeof(wm8900_reg_defaults));
>  }

I do not think that this was the intention of the original author,
I guess the idea behind sizeof(*codec->reg_cache) was to protect
the area behind it (in case wm8900_reg_defaults are badly defined).

re,
 wh

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