commit 36ae3c0a36b7456432fedce38ae2f7bd3e01a563
Author: Jan H. Schönherr <jschoenh@amazon.de>
Date:   Thu Sep 7 19:02:48 2017 +0100

    KVM: Don't accept obviously wrong gsi values via KVM_IRQFD

    We cannot add routes for gsi values >= KVM_MAX_IRQ_ROUTES -- see
    kvm_set_irq_routing(). Hence, there is no sense in accepting them
    via KVM_IRQFD. Prevent them from entering the system in the first
    place.

    Signed-off-by: Jan H. Schönherr <jschoenh@amazon.de>
    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index f2ac53a..c608ab4 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -565,6 +565,8 @@ kvm_irqfd(struct kvm *kvm, struct kvm_irqfd *args)
 {
 	if (args->flags & ~(KVM_IRQFD_FLAG_DEASSIGN | KVM_IRQFD_FLAG_RESAMPLE))
 		return -EINVAL;
+	if (args->gsi >= KVM_MAX_IRQ_ROUTES)
+		return -EINVAL;
 
 	if (args->flags & KVM_IRQFD_FLAG_DEASSIGN)
 		return kvm_irqfd_deassign(kvm, args);