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KVM: arm/arm64: vgic: Fix possible spectre-v1 write in vgic_mmio_write_apr()

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[ Upstream commit 6b8b9a4854 ]

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 <mark.rutland@arm.com>
Cc: Christoffer Dall <christoffer.dall@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: kvmarm@lists.cs.columbia.edu
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Mark Rutland 2018-07-10 19:01:23 +01:00 committed by Greg Kroah-Hartman
parent 3cb3868f98
commit 737066efec
1 changed files with 3 additions and 0 deletions
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3
virt/kvm/arm/vgic/vgic-mmio-v2.c
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@ -348,6 +348,9 @@ static void vgic_mmio_write_apr(struct kvm_vcpu *vcpu,
if (n > vgic_v3_max_apr_idx(vcpu))
return;
n = array_index_nospec(n, 4);
/* GICv3 only uses ICH_AP1Rn for memory mapped (GICv2) guests */
vgicv3->vgic_ap1r[n] = val;
}