linux-kernel - [PATCH 1/5] sound/isa/opti9xx/miro.c: eliminate possible double free

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Date:	Sun, 21 Oct 2012 12:52:03 +0200
From:	Julia Lawall <Julia.Lawall@...6.fr>
To:	Jaroslav Kysela <perex@...ex.cz>
Cc:	kernel-janitors@...r.kernel.org, Takashi Iwai <tiwai@...e.de>,
	alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/5] sound/isa/opti9xx/miro.c: eliminate possible double free

From: Julia Lawall <Julia.Lawall@...6.fr>

snd_miro_probe is a static function that is only called twice in the file
that defines it.  At each call site, its argument is freed using
snd_card_free.  Thus, there is no need for snd_miro_probe to call
snd_card_free on its argument on any of its error exit paths.

Because snd_card_free both reads the fields of its argument and kfrees its
argments, the results of the second snd_card_free should be unpredictable.

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

// <smpl>
@r@
identifier f,free,a;
parameter list[n] ps;
type T;
expression e;
@@

f(ps,T a,...) {
  ... when any
      when != a = e
  if(...) { ... free(a); ... return ...; }
  ... when any
}

@@
identifier r.f,r.free;
expression x,a;
expression list[r.n] xs;
@@

* x = f(xs,a,...);
  if (...) { ... free(a); ... return ...; }
// </smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@...6.fr>

---
Not tested.

 sound/isa/opti9xx/miro.c |    1 -
 1 file changed, 1 deletion(-)

diff --git a/sound/isa/opti9xx/miro.c b/sound/isa/opti9xx/miro.c
index 3d1afb6..4a7ff4e 100644
--- a/sound/isa/opti9xx/miro.c
+++ b/sound/isa/opti9xx/miro.c
@@ -1286,7 +1286,6 @@ static int __devinit snd_miro_probe(struct snd_card *card)
 
 	error = snd_card_miro_aci_detect(card, miro);
 	if (error < 0) {
-		snd_card_free(card);
 		snd_printk(KERN_ERR "unable to detect aci chip\n");
 		return -ENODEV;
 	}

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