int kvm_arch_prepare_memory_region(struct kvm *kvm,
				   struct kvm_memory_slot *memslot,
				   const struct kvm_userspace_memory_region *mem,
				   enum kvm_mr_change change)
{
	return kvmppc_core_prepare_memory_region(kvm, memslot, mem);
}

The product dereferences a pointer that it expects to be valid but is NULL.