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

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Message-ID: <s5hhbthywjl.wl%tiwai@suse.de>
Date:	Fri, 30 Oct 2009 12:02:22 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	Julia Lawall <julia@...u.dk>
Cc:	Kyle McMartin <kyle@...artin.ca>, Jaroslav Kysela <perex@...ex.cz>,
	linux-parisc@...r.kernel.org, alsa-devel@...a-project.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 3/14] sound/parisc: Move dereference after NULL test

At Sat, 17 Oct 2009 08:33:47 +0200 (CEST),
Julia Lawall wrote:
> 
> From: Julia Lawall <julia@...u.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@...u.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++) {
> 
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