KVM: arm/arm64: vgic: fix off-by-one bug in vgic_get_irq()

When using the nospec API, it should be taken into account that:

"...if the CPU speculates past the bounds check then
* array_index_nospec() will clamp the index within the range of [0,
* size)."

The above is part of the header for macro array_index_nospec() in linux/nospec.h

Now, in this particular case, if intid evaluates to exactly VGIC_MAX_SPI or to exaclty VGIC_MAX_PRIVATE, the array_index_nospec() macro ends up returning VGIC_MAX_SPI - 1 or VGIC_MAX_PRIVATE - 1 respectively, instead of VGIC_MAX_SPI or VGIC_MAX_PRIVATE, which, based on the original logic:

	/* SGIs and PPIs */
	if (intid <= VGIC_MAX_PRIVATE)

virt/kvm/arm/vgic/vgic.c +0 -0

 		return &vcpu->arch.vgic_cpu.private_irqs[intid];
 
 	/* SPIs */

if (intid <= VGIC_MAX_SPI)
return &kvm->arch.vgic.spis[intid - VGIC_NR_PRIVATE_IRQS];

are valid values for intid.

Fix this by calling array_index_nospec() macro with VGIC_MAX_PRIVATE + 1 and VGIC_MAX_SPI + 1 as arguments for its parameter size.

Fixes 41b87599c743 ("KVM: arm/arm64: vgic: fix possible spectre-v1 in vgic_get_irq()")

Cc [email protected]

Signed-off-by Gustavo A. R. Silva <[email protected]>

---
 virt/kvm/arm/vgic/vgic.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

virt/kvm/arm/vgic/vgic.c +1 -1

index 50e25438fb3c..5db40696055a 100644
@@ -103,13 +103,13 @@ struct vgic_irq *vgic_get_irq(struct kvm *kvm, struct kvm_vcpu *vcpu,
 {
 	/* SGIs and PPIs */
 	if (intid <= VGIC_MAX_PRIVATE) {
-		intid = array_index_nospec(intid, VGIC_MAX_PRIVATE);
+		intid = array_index_nospec(intid, VGIC_MAX_PRIVATE + 1);