4.20-stable review patch. If anyone has any objections, please let me know.
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From: Gustavo A. R. Silva gustavo@embeddedor.com
commit c23b2e6fc4ca346018618266bcabd335c0a8a49e upstream.
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@vger.kernel.org Signed-off-by: Gustavo A. R. Silva gustavo@embeddedor.com [dropped the SPI part which was fixed separately] Signed-off-by: Marc Zyngier marc.zyngier@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- virt/kvm/arm/vgic/vgic.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- 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 { /* 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]; }