KVM: Sanitize KVM_IRQFD flags

We only know of one so far.

Signed-off-by: Alex Williamson <[e-mail]>
Signed-off-by: Marcelo Tosatti <[e-mail]>

virt/kvm/eventfd.c

···
 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);