linux-kernel - Re: [PATCH] ASoC: soc-core: Add missing NULL check

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Date:   Fri, 9 Mar 2018 12:50:50 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Takashi Iwai <tiwai@...e.com>, Pavel Machek <pavel@....cz>,
        Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ASoC: soc-core: Add missing NULL check

On Thu, Mar 08, 2018 at 12:06:53PM -0800, Kees Cook wrote:

> If a codec is not attached to the sound soc, a NULL deref is possible as a
> regular user in /sys.

I can't parse this, sorry.  What is the "sound soc"?

> +++ b/sound/soc/soc-core.c
> @@ -137,6 +137,9 @@ static ssize_t soc_codec_reg_show(struct snd_soc_codec *codec, char *buf,
>  	size_t total = 0;
>  	loff_t p = 0;
>  
> +	if (!codec || !codec->driver)
> +		return 0;
> +

How are we managing to create a sysfs file for a CODEC which doesn't
have a CODEC struct associated with it?  That is obviously nonsensical
and suggests we've got some more serious problem going on here - if
there's no CODEC those sysfs attributes simply shouldn't be there.

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