[Intel-gfx] [CI 1/2] drm/i915/guc: Fix null pointer dereference when GuC FW is not available

[Michal Wajdeczko]

On Fri, 23 Mar 2018 13:07:15 +0100, Sagar Arun Kamble  
<sagar.a.kamble at intel.com> wrote:

>
>
> On 3/23/2018 4:53 PM, Piotr Piórkowski wrote:
>> If GuC firmware is not available on the system and we load i915 with  
>> enable
>> GuC, then we hit this null pointer dereference issue:
> Patch looks good but I have query on usage of enable_guc modparam.
> enable_guc modparam will enable GuC/HuC only if firmware is available.

During modparam sanitization phase, code will only check for firmware
name, code will attempt to check if firmware file exists.

> If user sets to forcefully enable GuC/HuC on systems that don't have  
> firmware then it is user's fault.

Sure its user's fault, but event in such case we should just gracefully
abort driver load, without any NULL pointer BUG ;)

And note, that we will hit this bug not only when user force GuC with:
	enable_guc=1 guc_firmware_path=/does/not/exist

but also when user just specify auto mode:
	enable_guc=-1

when predefined firmwares are not present (not installed or removed)

/m

> Michal, could you please clarify.
>