linux-kernel - Re: [PATCH] sound: hdmi: avoid dereferencing uninitialized 'jack' pointer

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Message-ID: <112888486.mQgaWiH0PI@wuerfel>
Date:	Tue, 16 Feb 2016 17:59:04 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Mark Brown <broonie@...nel.org>, Takashi Iwai <tiwai@...e.de>,
	alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
	Jaroslav Kysela <perex@...ex.cz>,
	David Henningsson <david.henningsson@...onical.com>,
	Han Lu <han.lu@...el.com>,
	Libin Yang <libin.yang@...ux.intel.com>,
	Thierry Reding <treding@...dia.com>
Subject: Re: [PATCH] sound: hdmi: avoid dereferencing uninitialized 'jack' pointer

On Tuesday 16 February 2016 16:38:40 Mark Brown wrote:
> On Tue, Feb 16, 2016 at 05:18:29PM +0100, Takashi Iwai wrote:
> > Arnd Bergmann wrote:
> 
> > > Another option might would be to change snd_jack_new() to return
> > > an error if that SND_JACK is disabled, and then require all users
> > > to handle the error gracefully, i.e. not fail the probe() function
> > > but just not use the jack.
> 
> > Yes, I thought of that, too.  If select is no good option, it's a good
> > alternative, indeed.
> 
> It's going to be a bunch of work to implement though.
> 

I've already sent a v2 to change the snd_jack_new() function, feel free
to ignore that. I also saw now that the same bug is present in hda_jack.c,
but I think the other drivers are fine.

How about this approach below? That should also make it possible to
use the jack APIs without using a error return.

	Arnd

diff --git a/sound/pci/hda/hda_jack.c b/sound/pci/hda/hda_jack.c
index a33234e04d4f..2f72b3c09d92 100644
--- a/sound/pci/hda/hda_jack.c
+++ b/sound/pci/hda/hda_jack.c
@@ -403,8 +403,10 @@ int snd_hda_jack_add_kctl(struct hda_codec *codec, hda_nid_t nid,
 
 	jack->phantom_jack = !!phantom_jack;
 	jack->type = type;
-	jack->jack->private_data = jack;
-	jack->jack->private_free = hda_free_jack_priv;
+	if (IS_ENABLED(CONFIG_SND_JACK)) {
+		jack->jack->private_data = jack;
+		jack->jack->private_free = hda_free_jack_priv;
+	}
 	state = snd_hda_jack_detect(codec, nid);
 	snd_jack_report(jack->jack, state ? jack->type : 0);
 
diff --git a/sound/pci/hda/patch_hdmi.c b/sound/pci/hda/patch_hdmi.c
index f4443b5fbf6e..e9a0f67c92ca 100644
--- a/sound/pci/hda/patch_hdmi.c
+++ b/sound/pci/hda/patch_hdmi.c
@@ -2532,8 +2532,10 @@ static int add_hdmi_jack_kctl(struct hda_codec *codec,
 		return err;
 
 	spec->pcm_rec[pcm_idx].jack = jack;
-	jack->private_data = &spec->pcm_rec[pcm_idx];
-	jack->private_free = free_hdmi_jack_priv;
+	if (IS_ENABLED(CONFIG_SND_JACK)) {
+		jack->private_data = &spec->pcm_rec[pcm_idx];
+		jack->private_free = free_hdmi_jack_priv;
+	}
 	return 0;
 }