RE: [PATCH] platform/x86: dell-wmi-sysman: fix a NULL pointer dereference

[Limonciello, Mario]

> -----Original Message-----
> From: Hans de Goede <hdegoede@xxxxxxxxxx>
> Sent: Saturday, January 30, 2021 15:44
> To: Limonciello, Mario; Mark Gross
> Cc: LKML; platform-driver-x86@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH] platform/x86: dell-wmi-sysman: fix a NULL pointer
> dereference
> 
> 
> [EXTERNAL EMAIL]
> 
> Hi,
> 
> On 1/29/21 6:26 PM, Mario Limonciello wrote:
> > An upcoming Dell platform is causing a NULL pointer dereference
> > in dell-wmi-sysman initialization.  Validate that the input from
> > BIOS matches correct ACPI types and abort module initialization
> > if it fails.
> >
> > This leads to a memory leak that needs to be cleaned up properly.
> >
> > Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxxx>
> > ---
> >  drivers/platform/x86/dell-wmi-sysman/sysman.c | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/platform/x86/dell-wmi-sysman/sysman.c
> b/drivers/platform/x86/dell-wmi-sysman/sysman.c
> > index dc6dd531c996..38b497991071 100644
> > --- a/drivers/platform/x86/dell-wmi-sysman/sysman.c
> > +++ b/drivers/platform/x86/dell-wmi-sysman/sysman.c
> > @@ -419,13 +419,19 @@ static int init_bios_attributes(int attr_type, const
> char *guid)
> >  		return retval;
> >  	/* need to use specific instance_id and guid combination to get right
> data */
> >  	obj = get_wmiobj_pointer(instance_id, guid);
> > -	if (!obj)
> > +	if (!obj || obj->type != ACPI_TYPE_PACKAGE) {
> > +		release_attributes_data();
> 
> All calls of  init_bios_attributes() have the following error handling:
> 
>         ret = init_bios_attributes(INT, DELL_WMI_BIOS_INTEGER_ATTRIBUTE_GUID);
>         if (ret) {
>                 pr_debug("failed to populate integer type attributes\n");
>                 goto fail_create_group;
>         }
> 
> 	...
> 
> fail_create_group:
>         release_attributes_data();
> 
> So that added release_attributes_data() call is not necessary. If you can
> respin
> this patch Monday with the release_attributes_data(); addition dropped, then
> I will try to get this to Linus in time for 5.11 .
> 
> Or I can fix this up locally if you agree with dropping the unnecessary
> release_attributes_data() call.
> 

Yes, please go ahead and drop the unnecessary call locally.

Thank you

> Regards,
> 
> Hans
> 
> 
> 
> 
> >  		return -ENODEV;
> > +	}
> >  	elements = obj->package.elements;
> >
> >  	mutex_lock(&wmi_priv.mutex);
> >  	while (elements) {
> >  		/* sanity checking */
> > +		if (elements[ATTR_NAME].type != ACPI_TYPE_STRING) {
> > +			pr_debug("incorrect element type\n");
> > +			goto nextobj;
> > +		}
> >  		if (strlen(elements[ATTR_NAME].string.pointer) == 0) {
> >  			pr_debug("empty attribute found\n");
> >  			goto nextobj;
> >