From: "Gustavo A. R. Silva" <gustavo@xxxxxxxxxxxxxx>
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)
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: stable@xxxxxxxxxxxxxxx
Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>
[dropped the SPI part which was fixed separately]
Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
---
virt/kvm/arm/vgic/vgic.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
index 8ab0491bcc94..f884a54b2601 100644
--- a/virt/kvm/arm/vgic/vgic.c
+++ b/virt/kvm/arm/vgic/vgic.c
@@ -103,7 +103,7 @@ 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);
return &vcpu->arch.vgic_cpu.private_irqs[intid];
}
--
2.19.2
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