linux-kernel - RE: [PATCH] Subject: Prevent acpi_run_osc from using NULL objects (was: Re: Oops in ACPI with git latest)

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Date:	Fri, 24 Oct 2008 08:02:37 -0700
From:	"Moore, Robert" <robert.moore@...el.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>
CC:	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Len Brown <lenb@...nel.org>
Subject: RE: [PATCH] Subject: Prevent acpi_run_osc from using NULL objects
 (was: Re: Oops in ACPI with git latest)


>> Still, I'd expect the AML interpreter to return error code in this case.


We've just recently deployed a new module that validates the inputs and outputs for the predefined ACPI methods (Those that start with underscore).

That is the source of these messages:

> > ACPI Warning (nspredef-0252): \_SB_.PCI0._OSC: Parameter count mismatch - ASL declared 5, expected 4 [20080926]
> > ACPI Error (nspredef-0163): \_SB_.PCI0._OSC: Missing expected return value [20080926]

For the initial version of this module, we only output messages when the inputs and/or outputs don't match the requirements of the ACPI specification. 

We can change this to returning exceptions in the future.
 

>-----Original Message-----
>From: linux-acpi-owner@...r.kernel.org [mailto:linux-acpi-
>owner@...r.kernel.org] On Behalf Of Rafael J. Wysocki
>Sent: Friday, October 24, 2008 4:50 AM
>To: James Bottomley; Jesse Barnes
>Cc: Moore, Robert; linux-acpi@...r.kernel.org; linux-kernel; Len Brown
>Subject: [PATCH] Subject: Prevent acpi_run_osc from using NULL objects
>(was: Re: Oops in ACPI with git latest)
>
>On Friday, 24 of October 2008, Rafael J. Wysocki wrote:
>> On Friday, 24 of October 2008, James Bottomley wrote:
>> > On Thu, 2008-10-23 at 15:34 -0700, Moore, Robert wrote:
>> > > +	if (!output.pointer)
>> > > +		return AE_NULL_OBJECT;
>> > > +
>> > >
>> > > This probably won't work. acpi_evaluate_object currently doesn't
>touch the pointer parameter if there is no return value, it only sets the
>length to zero.
>> >
>> > Actually, it does.
>>
>> Well, this was the only candidate for a NULL pointer dereference, so I'd
>be
>> surprised if it didn't. :-)
>>
>> > > So, you might try this:
>> > >
>> > > +	if (!output.length)
>> > > +		return AE_NULL_OBJECT;
>> > > +
>>
>> Still, I'd expect the AML interpreter to return error code in this case.
>>
>> > This also works.
>>
>> Why don't we make it extra safe, then. ;-)
>>
>> ---
>> From: Rafael J. Wysocki <rjw@...k.pl>
>> Subject: Prevent acpi_osc_run from using NULL objects
>
>Ah, mistake in the subject.
>
>---
>From: Rafael J. Wysocki <rjw@...k.pl>
>Subject: Prevent acpi_run_osc from using NULL objects
>
>Check if the object returned by acpi_evaluate_object() in
>acpi_run_osc() is not NULL before using it.
>
>Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
>---
> drivers/pci/pci-acpi.c |    3 +++
> 1 file changed, 3 insertions(+)
>
>Index: linux-2.6/drivers/pci/pci-acpi.c
>===================================================================
>--- linux-2.6.orig/drivers/pci/pci-acpi.c
>+++ linux-2.6/drivers/pci/pci-acpi.c
>@@ -83,6 +83,9 @@ static acpi_status acpi_run_osc(acpi_han
> 	if (ACPI_FAILURE(status))
> 		return status;
>
>+	if (!output.pointer || !output.length)
>+		return AE_NULL_OBJECT;
>+
> 	out_obj = output.pointer;
> 	if (out_obj->type != ACPI_TYPE_BUFFER) {
> 		printk(KERN_DEBUG "Evaluate _OSC returns wrong type\n");
>--
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