linux-kernel - RE: [PATCH] ASoC: Intel: fix possible acpi enumeration panic

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Date:	Thu, 11 Dec 2014 21:55:38 +0000
From:	"Strasser, Kevin" <kevin.strasser@...el.com>
To:	Mark Brown <broonie@...nel.org>
CC:	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	"Koul, Vinod" <vinod.koul@...el.com>,
	"Lin, Mengdong" <mengdong.lin@...el.com>,
	"Fang, Yang A" <yang.a.fang@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] ASoC: Intel: fix possible acpi enumeration panic

> -----Original Message-----
> From: Mark Brown [mailto:broonie@...nel.org]
> Sent: Thursday, December 11, 2014 5:20 AM> 
> On Wed, Dec 10, 2014 at 11:21:57PM -0800, Kevin Strasser wrote:
> 
> > A crash can occur on some platforms where adsp is enumerated but codec
> > is not matched. Check that the codec_id string is valid before
> > attempting to match.
> 
> > -	for (mach = machines; mach->codec_id; mach++)
> > +	for (mach = machines; mach->codec_id[0]; mach++)
> 
> This changes the check from verifying if a codec_id is present to verifying if
> the first character in the codec_id is non-NULL.  That doesn't seem obviously
> safer and the tables of machines seem to be terminated by having an entry
> with all fields set to zero (which is a common idiom in Linux) which would
> now crash with this change.

In this case mach->codec_id is non-NULL, even for the terminating element, because it
is defined to be a fixed width. So we have to take a look at the first character to see if it
has been initialized.

-Kevin
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