linux-kernel - [PATCH v2 5/6] KVM: x86: prevent setup of invalid routes

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Date:   Fri, 16 Dec 2016 16:10:05 +0100
From:   Radim Krčmář <rkrcmar@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH v2 5/6] KVM: x86: prevent setup of invalid routes

The check in kvm_set_pic_irq() and kvm_set_ioapic_irq() was just a
temporary measure until the code improved enough for us to do this.

This changes APIC in a case when KVM_SET_GSI_ROUTING is called to set up pic
and ioapic routes before KVM_CREATE_IRQCHIP.  Those rules would get overwritten
by KVM_CREATE_IRQCHIP at best, so it is pointless to allow it.  Userspaces
hopefully noticed that things don't work if they do that and don't do that.

Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
---
 v2: r-b Paolo
---
 arch/x86/kvm/irq_comm.c | 19 ++++++-------------
 1 file changed, 6 insertions(+), 13 deletions(-)

diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c
index 1dfeb185a1e3..2639b8d3dce2 100644
--- a/arch/x86/kvm/irq_comm.c
+++ b/arch/x86/kvm/irq_comm.c
@@ -41,15 +41,6 @@ static int kvm_set_pic_irq(struct kvm_kernel_irq_routing_entry *e,
 			   bool line_status)
 {
 	struct kvm_pic *pic = pic_irqchip(kvm);
-
-	/*
-	 * XXX: rejecting pic routes when pic isn't in use would be better,
-	 * but the default routing table is installed while kvm->arch.vpic is
-	 * NULL and KVM_CREATE_IRQCHIP can race with KVM_IRQ_LINE.
-	 */
-	if (!pic)
-		return -1;
-
 	return kvm_pic_set_irq(pic, e->irqchip.pin, irq_source_id, level);
 }
 
@@ -58,10 +49,6 @@ static int kvm_set_ioapic_irq(struct kvm_kernel_irq_routing_entry *e,
 			      bool line_status)
 {
 	struct kvm_ioapic *ioapic = kvm->arch.vioapic;
-
-	if (!ioapic)
-		return -1;
-
 	return kvm_ioapic_set_irq(ioapic, e->irqchip.pin, irq_source_id, level,
 				line_status);
 }
@@ -301,10 +288,16 @@ int kvm_set_routing_entry(struct kvm *kvm,
 			delta = 8;
 			/* fall through */
 		case KVM_IRQCHIP_PIC_MASTER:
+			if (!pic_in_kernel(kvm))
+				goto out;
+
 			e->set = kvm_set_pic_irq;
 			max_pin = PIC_NUM_PINS;
 			break;
 		case KVM_IRQCHIP_IOAPIC:
+			if (!ioapic_in_kernel(kvm))
+				goto out;
+
 			max_pin = KVM_IOAPIC_NUM_PINS;
 			e->set = kvm_set_ioapic_irq;
 			break;
-- 
2.11.0