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@xxxxxxx>
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@xxxxxxx>
---
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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