From: jschoenh@amazon.de
Date: Thu, 7 Sep 2017 19:02:30 +0100
Subject: [PATCH 1/2] KVM: VMX: Do not BUG() on out-of-bounds guest IRQ
Git-commit: 3a8b0677fc6180a467e26cc32ce6b0c09a32f9bb
Patch-mainline: v4.14-rc1
References: bsc#1058038, CVE-2017-1000252

The value of the guest_irq argument to vmx_update_pi_irte() is
ultimately coming from a KVM_IRQFD API call. Do not BUG() in
vmx_update_pi_irte() if the value is out-of bounds. (Especially,
since KVM as a whole seems to hang after that.)

Instead, WARN_ONCE() if we find that we don't have a route for a
certain IRQ (which can be out-of-bounds or within the array).

Signed-off-by: Jan H. Schönherr <jschoenh@amazon.de>
Acked-by: Joerg Roedel <jroedel@suse.de>
---
 arch/x86/kvm/vmx.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -11370,7 +11370,7 @@ static int vmx_update_pi_irte(struct kvm
 	struct kvm_lapic_irq irq;
 	struct kvm_vcpu *vcpu;
 	struct vcpu_data vcpu_info;
-	int idx, ret = -EINVAL;
+	int idx, ret = 0;
 
 	if (!kvm_arch_has_assigned_device(kvm) ||
 		!irq_remapping_cap(IRQ_POSTING_CAP) ||
@@ -11379,7 +11379,12 @@ static int vmx_update_pi_irte(struct kvm
 
 	idx = srcu_read_lock(&kvm->irq_srcu);
 	irq_rt = srcu_dereference(kvm->irq_routing, &kvm->irq_srcu);
-	BUG_ON(guest_irq >= irq_rt->nr_rt_entries);
+	if (guest_irq >= irq_rt->nr_rt_entries ||
+	    hlist_empty(&irq_rt->map[guest_irq])) {
+		WARN_ONCE(1, "no route for guest_irq %u/%u (broken user space?)\n",
+			  guest_irq, irq_rt->nr_rt_entries);
+		goto out;
+	}
 
 	hlist_for_each_entry(e, &irq_rt->map[guest_irq], link) {
 		if (e->type != KVM_IRQ_ROUTING_MSI)