drm/i915/guc: Clear pointers on free

Clear out some pointers when objects have been de-allocated. This
makes it much easier to track down use-after-free type issues.
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201028145826.2949180-4-John.C.Harrison@Intel.com

drivers/gpu/drm/i915/gt/uc/intel_guc_ads.c

@@ -220,6 +220,7 @@ int intel_guc_ads_create(struct intel_guc *guc)
 void intel_guc_ads_destroy(struct intel_guc *guc)
 {
 	i915_vma_unpin_and_release(&guc->ads_vma, I915_VMA_RELEASE_MAP);
+	guc->ads_blob = NULL;
 }
 
 static void guc_ads_private_data_reset(struct intel_guc *guc)

drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c

@@ -210,6 +210,7 @@ void intel_guc_ct_fini(struct intel_guc_ct *ct)
 	GEM_BUG_ON(ct->enabled);
 
 	i915_vma_unpin_and_release(&ct->vma, I915_VMA_RELEASE_MAP);
+	memset(ct, 0, sizeof(*ct));
 }
 
 /**