[PATCH] ASoC: Intel: fix possible acpi enumeration panic

[PATCH] ASoC: Intel: fix possible acpi enumeration panic

[Kevin Strasser]

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.

Signed-off-by: Kevin Strasser <kevin.strasser@intel.com>
---
 sound/soc/intel/sst/sst_acpi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/soc/intel/sst/sst_acpi.c b/sound/soc/intel/sst/sst_acpi.c
index 31124aa..dd72e58 100644
--- a/sound/soc/intel/sst/sst_acpi.c
+++ b/sound/soc/intel/sst/sst_acpi.c
@@ -236,7 +236,7 @@ static struct sst_machines *sst_acpi_find_machine(
 	struct sst_machines *mach;
 	bool found = false;
 
-	for (mach = machines; mach->codec_id; mach++)
+	for (mach = machines; mach->codec_id[0]; mach++)
 		if (ACPI_SUCCESS(acpi_get_devices(mach->codec_id,
 						  sst_acpi_mach_match,
 						  &found, NULL)) && found)
-- 
1.9.1

Re: [PATCH] ASoC: Intel: fix possible acpi enumeration panic

[Mark Brown]

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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.

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

[Strasser, Kevin]

> -----Original Message-----
> From: Mark Brown [mailto:broonie@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

Re: [PATCH] ASoC: Intel: fix possible acpi enumeration panic

[Mark Brown]

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On Thu, Dec 11, 2014 at 09:55:38PM +0000, Strasser, Kevin wrote:

Please fix your mailer to word wrap comfortably under 80 colums so that
your mails are easily legible.

> > 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.

That's a really unusual and (as you've seen) error prone idiom - is it
not better to fix the struct to use the more common idiom?

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Re: [PATCH] ASoC: Intel: fix possible acpi enumeration panic

[Mark Brown]

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On Thu, Dec 11, 2014 at 09:55:38PM +0000, Strasser, Kevin wrote:

Please fix your mailer to word wrap comfortably under 80 colums so that
your mails are easily legible.

> > 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.

That's a really unusual and (as you've seen) error prone idiom - is it
not better to fix the struct to use the more common idiom?

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

[Kevin Strasser]

On Mon, Dec 15, 2014 at 05:06:45PM +0000, Mark Brown wrote:
> Please fix your mailer to word wrap comfortably under 80 colums so that your
> mails are easily legible.

Understood

> > > 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.
> 
> That's a really unusual and (as you've seen) error prone idiom - is it not
> better to fix the struct to use the more common idiom?

That seems like a good idea to me. I'll prepare a new patch to change the
sst_machines definition so that codec_id gets initialized to NULL.

-Kevin

[PATCH v2] ASoC: Intel: fix possible acpi enumeration panic

[Kevin Strasser]

A crash can occur on some platforms where adsp is enumerated but codec is not
matched. Define codec_id as a pointer intead of an array so that it gets
initialized to NULL for the terminating element of sst_acpi_bytcr[] and
sst_acpi_chv[].

Signed-off-by: Kevin Strasser <kevin.strasser@linux.intel.com>
---
 sound/soc/intel/sst/sst_acpi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/soc/intel/sst/sst_acpi.c b/sound/soc/intel/sst/sst_acpi.c
index 31124aa..87b5090 100644
--- a/sound/soc/intel/sst/sst_acpi.c
+++ b/sound/soc/intel/sst/sst_acpi.c
@@ -43,7 +43,7 @@
 #include "sst.h"
 
 struct sst_machines {
-	char codec_id[32];
+	char *codec_id;
 	char board[32];
 	char machine[32];
 	void (*machine_quirk)(void);
-- 
1.9.1

Re: [PATCH v2] ASoC: Intel: fix possible acpi enumeration panic

[Mark Brown]

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On Mon, Dec 15, 2014 at 04:15:04PM -0800, Kevin Strasser wrote:
> A crash can occur on some platforms where adsp is enumerated but codec is not
> matched. Define codec_id as a pointer intead of an array so that it gets
> initialized to NULL for the terminating element of sst_acpi_bytcr[] and
> sst_acpi_chv[].

Applied, thanks.

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