Commit 5e1ca5e2 authored Apr 25, 2018 by Mark Rutland Committed by Will Deacon Apr 26, 2018

KVM: arm/arm64: vgic: fix possible spectre-v1 in vgic_mmio_read_apr()



It's possible for userspace to control n. Sanitize n when using it as an
array index.

Note that while it appears that n must be bound to the interval [0,3]
due to the way it is extracted from addr, we cannot guarantee that
compiler transformations (and/or future refactoring) will ensure this is
the case, and given this is a slow path it's better to always perform
the masking.

Found by smatch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Christoffer Dall <christoffer.dall@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: kvmarm@lists.cs.columbia.edu
Signed-off-by: Will Deacon <will.deacon@arm.com>

parent 41b87599

virt/kvm/arm/vgic/vgic-mmio-v2.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -14,6 +14,8 @@
		#include <linux/irqchip/arm-gic.h>
		#include <linux/kvm.h>
		#include <linux/kvm_host.h>
		#include <linux/nospec.h>

		#include <kvm/iodev.h>
		#include <kvm/arm_vgic.h>

		@@ -324,6 +326,9 @@ static unsigned long vgic_mmio_read_apr(struct kvm_vcpu *vcpu,

		if (n > vgic_v3_max_apr_idx(vcpu))
		return 0;

		n = array_index_nospec(n, 4);

		/* GICv3 only uses ICH_AP1Rn for memory mapped (GICv2) guests */
		return vgicv3->vgic_ap1r[n];
		}