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

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Message-ID: <20180309193523.GA2977@amd>
Date:   Fri, 9 Mar 2018 20:35:23 +0100
From:   Pavel Machek <pavel@....cz>
To:     Kees Cook <keescook@...omium.org>
Cc:     Mark Brown <broonie@...nel.org>, Takashi Iwai <tiwai@...e.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        moderated for non-subscribers <alsa-devel@...a-project.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ASoC: soc-core: Add missing NULL check

On Fri 2018-03-09 10:45:16, Kees Cook wrote:
> On Fri, Mar 9, 2018 at 4:50 AM, Mark Brown <broonie@...nel.org> wrote:
> > 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"?
> 
> SoC's sound component? I'm not sure either. :) I was just sending the
> patch that I mentioned from the thread where Pavel mentioned this
> Oops.
> 
> Pavel, can you isolate the specific file that is causing the oops?
> (Maybe this patch should be a WARN() instead of silent return 0, since
> we still don't want to crash, but it should be considered a bug...)

Crash is reproducible on linux-next on Nokia N900. But I seen hang on
Nokia N9, with different kernel, that may be related.

And yes, WARN() would be nicer.

> >> +++ 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.
> 
> No idea! Hopefully Pavel has more details...

Pavel probably can reproduce it...

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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