> Since acpi_evaluate_object doesn't set the pointer value, it may be simply
> random.
>
> >-----Original Message-----
> >From: Rafael J. Wysocki [mailto:rjw@sisk.pl]
> >Sent: Thursday, October 23, 2008 11:57 PM
> >To: James Bottomley; Jesse Barnes
> >Cc: Moore, Robert; linux-acpi@vger.kernel.org; linux-kernel; Len Brown
> >Subject: Re: Oops in ACPI with git latest
> >
> >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@sisk.pl>
> >Subject: Prevent acpi_osc_run from using NULL objects
> >
> >Check if the object returned by acpi_evaluate_object() in
> >acpi_run_osc() is not NULL.
> >
> >Signed-off-by: Rafael J. Wysocki <rjw@sisk.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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