KVM: Sanitize KVM_IRQFD flags

We only know of one so far.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

virt/kvm/eventfd.c

@@ -340,6 +340,9 @@ kvm_irqfd_deassign(struct kvm *kvm, struct kvm_irqfd *args)
 int
 kvm_irqfd(struct kvm *kvm, struct kvm_irqfd *args)
 {
+	if (args->flags & ~KVM_IRQFD_FLAG_DEASSIGN)
+		return -EINVAL;
+
 	if (args->flags & KVM_IRQFD_FLAG_DEASSIGN)
 		return kvm_irqfd_deassign(kvm, args);