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

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Date:	Wed, 24 Feb 2016 17:18:58 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Takashi Iwai <tiwai@...e.de>, alsa-devel@...a-project.org,
	linux-kernel@...r.kernel.org, Jaroslav Kysela <perex@...ex.cz>,
	Mark Brown <broonie@...nel.org>,
	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 Wednesday 17 February 2016 10:35:40 Takashi Iwai wrote:
> On Wed, 17 Feb 2016 10:03:50 +0100,
> +	const char *id;
> +#ifdef CONFIG_SND_JACK_INPUT_DEV
> +	struct input_dev *input_dev;
>  	int registered;
>  	int type;
> -	const char *id;
>  	char name[100];
>  	unsigned int key[6];   /* Keep in sync with definitions above */
> +#endif /* CONFIG_SND_JACK_INPUT_DEV */
>  	void *private_data;
>  	void (*private_free)(struct snd_jack *);
>  };

I got a build error from this today, as the trace event tries to print
the jack "name" field. I've managed to get it to build again by printing
the "id" field in place of the "name". The name is normally assigned
from id in snd_jack_dev_register using

        snprintf(jack->name, sizeof(jack->name), "%s %s",
                 card->shortname, jack->id);

but that code is not called here at all. My patch will slightly
alter the output as a consequence, but I don't know if this change
is critical or not.

	Arnd

diff --git a/include/trace/events/asoc.h b/include/trace/events/asoc.h
index 317a1ed2f4ac..9130dd5a184a 100644
--- a/include/trace/events/asoc.h
+++ b/include/trace/events/asoc.h
@@ -231,13 +231,13 @@ TRACE_EVENT(snd_soc_jack_report,
 	TP_ARGS(jack, mask, val),
 
 	TP_STRUCT__entry(
-		__string(	name,		jack->jack->name	)
+		__string(	name,		jack->jack->id		)
 		__field(	int,		mask			)
 		__field(	int,		val			)
 	),
 
 	TP_fast_assign(
-		__assign_str(name, jack->jack->name);
+		__assign_str(name, jack->jack->id);
 		__entry->mask = mask;
 		__entry->val = val;
 	),
@@ -253,12 +253,12 @@ TRACE_EVENT(snd_soc_jack_notify,
 	TP_ARGS(jack, val),
 
 	TP_STRUCT__entry(
-		__string(	name,		jack->jack->name	)
+		__string(	name,		jack->jack->id		)
 		__field(	int,		val			)
 	),
 
 	TP_fast_assign(
-		__assign_str(name, jack->jack->name);
+		__assign_str(name, jack->jack->id);
 		__entry->val = val;
 	),