[alsa-devel] [PATCH] ASoC: Intel: fix possible acpi enumeration panic

[Strasser, Kevin]

> -----Original Message-----
> From: Mark Brown [mailto:broonie at kernel.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