From 93cfad8da7164b095b2402ec9b2067fa15d6f250 Mon Sep 17 00:00:00 2001 From: Sascha Bischoff Date: Tue, 11 Aug 2026 15:10:47 +0000 Subject: [PATCH] KVM: arm64: vgic: Prevent speculative SPI array underflow For a non-GICv5 VM, SPI interrupt IDs include the private-interrupt offset, while KVM's SPI array is indexed from zero. The lookup applies array_index_nospec() to the absolute interrupt ID and subtracts the private-interrupt offset afterwards. On a speculative bypass of the range check for an interrupt ID below the private range, the clamp preserves the small absolute value and the subtraction underflows to an out-of-bounds SPI array index. Convert the interrupt ID to a zero-based index into the SPI array before applying array_index_nospec(). This way, we ensure that we clamp to a reachable SPI ID, rather than an out-of-range SPI index. Fixes: 41b87599c743 ("KVM: arm/arm64: vgic: fix possible spectre-v1 in vgic_get_irq()") Link: https://sashiko.dev/#/patchset/20260724104819.1296803-1-sascha.bischoff@arm.com?part=27 Signed-off-by: Sascha Bischoff Reviewed-by: Joey Gouly Reviewed-by: Marc Zyngier Link: https://patch.msgid.link/20260811150941.941295-3-sascha.bischoff@arm.com Signed-off-by: Oliver Upton --- arch/arm64/kvm/vgic/vgic.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kvm/vgic/vgic.c b/arch/arm64/kvm/vgic/vgic.c index 5a4768d8cd4f..3077cfdaa146 100644 --- a/arch/arm64/kvm/vgic/vgic.c +++ b/arch/arm64/kvm/vgic/vgic.c @@ -93,8 +93,9 @@ struct vgic_irq *vgic_get_irq(struct kvm *kvm, u32 intid) /* SPIs */ if (intid >= VGIC_NR_PRIVATE_IRQS && intid < (kvm->arch.vgic.nr_spis + VGIC_NR_PRIVATE_IRQS)) { - intid = array_index_nospec(intid, kvm->arch.vgic.nr_spis + VGIC_NR_PRIVATE_IRQS); - return &kvm->arch.vgic.spis[intid - VGIC_NR_PRIVATE_IRQS]; + intid -= VGIC_NR_PRIVATE_IRQS; + intid = array_index_nospec(intid, kvm->arch.vgic.nr_spis); + return &kvm->arch.vgic.spis[intid]; } /* LPIs */