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Subject[PATCH 4.18 063/235] KVM: arm/arm64: vgic: Fix possible spectre-v1 write in vgic_mmio_write_apr()
4.18-stable review patch.  If anyone has any objections, please let me know.


From: Mark Rutland <>

[ Upstream commit 6b8b9a48545e08345b8ff77c9fd51b1aebdbefb3 ]

It's possible for userspace to control n. Sanitize n when using it as an
array index, to inhibit the potential spectre-v1 write gadget.

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 <>
Cc: Christoffer Dall <>
Cc: Marc Zyngier <>
Signed-off-by: Marc Zyngier <>
Signed-off-by: Sasha Levin <>
Signed-off-by: Greg Kroah-Hartman <>
virt/kvm/arm/vgic/vgic-mmio-v2.c | 3 +++
1 file changed, 3 insertions(+)

--- a/virt/kvm/arm/vgic/vgic-mmio-v2.c
+++ b/virt/kvm/arm/vgic/vgic-mmio-v2.c
@@ -352,6 +352,9 @@ static void vgic_mmio_write_apr(struct k

if (n > vgic_v3_max_apr_idx(vcpu))
+ n = array_index_nospec(n, 4);
/* GICv3 only uses ICH_AP1Rn for memory mapped (GICv2) guests */
vgicv3->vgic_ap1r[n] = val;

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