[PATCH 3/14] sound/parisc: Move dereference after NULL test

[PATCH 3/14] sound/parisc: Move dereference after NULL test

[Julia Lawall]

From: Julia Lawall <julia@diku.dk>

If the NULL test on h is needed in snd_harmony_mixer_init, then the
dereference should be after the NULL test.

Actually, there is a sequence of calls: snd_harmony_create, then
snd_harmony_pcm_init, and then snd_harmony_mixer_init.  snd_harmony_create
initializes h, but may indeed leave it as NULL.  There was no NULL test at
the beginning of snd_harmony_pcm_init, so I have added one.  The NULL test
in snd_harmony_mixer_init is then not necessary, but in case the ordering
of the calls changes, I have left it, and moved the dereference after it.

A simplified version of the semantic match that detects this problem is as
follows (http://coccinelle.lip6.fr/):

// <smpl>
@match exists@
expression x, E;
identifier fld;
@@

* x->fld
  ... when != \(x = E\|&x\)
* x == NULL
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>

---
 sound/parisc/harmony.c              |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/sound/parisc/harmony.c b/sound/parisc/harmony.c
index e924492..f47f9e2 100644
--- a/sound/parisc/harmony.c
+++ b/sound/parisc/harmony.c
@@ -624,6 +624,9 @@ snd_harmony_pcm_init(struct snd_harmony *h)
 	struct snd_pcm *pcm;
 	int err;
 
+	if (snd_BUG_ON(!h))
+		return -EINVAL;
+
 	harmony_disable_interrupts(h);
 	
    	err = snd_pcm_new(h->card, "harmony", 0, 1, 1, &pcm);
@@ -865,11 +868,12 @@ snd_harmony_mixer_reset(struct snd_harmony *h)
 static int __devinit
 snd_harmony_mixer_init(struct snd_harmony *h)
 {
-	struct snd_card *card = h->card;
+	struct snd_card *card;
 	int idx, err;
 
 	if (snd_BUG_ON(!h))
 		return -EINVAL;
+	card = h->card;
 	strcpy(card->mixername, "Harmony Gain control interface");
 
 	for (idx = 0; idx < HARMONY_CONTROLS; idx++) {

Re: [PATCH 3/14] sound/parisc: Move dereference after NULL test

[Takashi Iwai]

At Sat, 17 Oct 2009 08:33:47 +0200 (CEST),
Julia Lawall wrote:
> 
> From: Julia Lawall <julia@diku.dk>
> 
> If the NULL test on h is needed in snd_harmony_mixer_init, then the
> dereference should be after the NULL test.
> 
> Actually, there is a sequence of calls: snd_harmony_create, then
> snd_harmony_pcm_init, and then snd_harmony_mixer_init.  snd_harmony_create
> initializes h, but may indeed leave it as NULL.  There was no NULL test at
> the beginning of snd_harmony_pcm_init, so I have added one.  The NULL test
> in snd_harmony_mixer_init is then not necessary, but in case the ordering
> of the calls changes, I have left it, and moved the dereference after it.
> 
> A simplified version of the semantic match that detects this problem is as
> follows (http://coccinelle.lip6.fr/):
> 
> // <smpl>
> @match exists@
> expression x, E;
> identifier fld;
> @@
> 
> * x->fld
>   ... when != \(x = E\|&x\)
> * x == NULL
> // </smpl>
> 
> Signed-off-by: Julia Lawall <julia@diku.dk>

Applied this one, too.  Thanks.


Takashi


> ---
>  sound/parisc/harmony.c              |    6 +++++-
>  1 files changed, 5 insertions(+), 1 deletions(-)
> 
> diff --git a/sound/parisc/harmony.c b/sound/parisc/harmony.c
> index e924492..f47f9e2 100644
> --- a/sound/parisc/harmony.c
> +++ b/sound/parisc/harmony.c
> @@ -624,6 +624,9 @@ snd_harmony_pcm_init(struct snd_harmony *h)
>  	struct snd_pcm *pcm;
>  	int err;
>  
> +	if (snd_BUG_ON(!h))
> +		return -EINVAL;
> +
>  	harmony_disable_interrupts(h);
>  	
>     	err = snd_pcm_new(h->card, "harmony", 0, 1, 1, &pcm);
> @@ -865,11 +868,12 @@ snd_harmony_mixer_reset(struct snd_harmony *h)
>  static int __devinit
>  snd_harmony_mixer_init(struct snd_harmony *h)
>  {
> -	struct snd_card *card = h->card;
> +	struct snd_card *card;
>  	int idx, err;
>  
>  	if (snd_BUG_ON(!h))
>  		return -EINVAL;
> +	card = h->card;
>  	strcpy(card->mixername, "Harmony Gain control interface");
>  
>  	for (idx = 0; idx < HARMONY_CONTROLS; idx++) {
> 

Re: [PATCH 3/14] sound/parisc: Move dereference after NULL test

[Kyle McMartin]

On Fri, Oct 30, 2009 at 12:02:22PM +0100, Takashi Iwai wrote:
> At Sat, 17 Oct 2009 08:33:47 +0200 (CEST),
> Julia Lawall wrote:
> > 
> > From: Julia Lawall <julia@diku.dk>
> > 
> > Signed-off-by: Julia Lawall <julia@diku.dk>
> 
> Applied this one, too.  Thanks.
> 
> 

Great, thanks Takashi!

cheers, Kyle