2009-12-13 11:43:24

by Julia Lawall

Subject: [PATCH 9/9] sound/soc/codecs: Correct code taking the size of a pointer

From: Julia Lawall <[email protected]>

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 <[email protected]>

---
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));
}

static int wm8900_hp_event(struct snd_soc_dapm_widget *w,

2009-12-13 14:09:35

by walter harms

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

Julia Lawall schrieb:
> From: Julia Lawall <[email protected]>
>
> 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 <[email protected]>
>
> ---
> 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

2009-12-13 15:21:24

by Julia Lawall

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

On Sun, 13 Dec 2009, walter harms wrote:

>
>
> Julia Lawall schrieb:
> > From: Julia Lawall <[email protected]>
> >
> > 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 <[email protected]>
> >
> > ---
> > 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).

sizeof(codec->reg_cache) is the size of a pointer (void *).
sizeof(*codec->reg_cache) is then the size of void. wm8900_reg_defaults
is a static constant array defined a few lines before this code:

static const u16 wm8900_reg_defaults[WM8900_MAXREG] = { ... };

Later in the same file there is:

cache = kmemdup(codec->reg_cache, sizeof(wm8900_reg_defaults),
GFP_KERNEL);

and codec->reg_cache is initialized as follows:

codec->reg_cache = &wm8900->reg_cache[0];

The reg_cache field in wm8900 is declared as u16 reg_cache[WM8900_MAXREG];

julia

2009-12-14 11:38:54

by Mark Brown

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

On Sun, Dec 13, 2009 at 12:43:15PM +0100, Julia Lawall wrote:
> From: Julia Lawall <[email protected]>
>
> 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.

Applied, thanks.