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KVM: x86: Protect MSR-based index computations in fixed_msr_to_seg_unit() from Spectre-v1/L1TF attacks

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This fixes a Spectre-v1/L1TF vulnerability in fixed_msr_to_seg_unit().
This function contains index computations based on the
(attacker-controlled) MSR number.

Fixes: de9aef5e1a ("KVM: MTRR: introduce fixed_mtrr_segment table")

Signed-off-by: Nick Finco <nifi@google.com>
Signed-off-by: Marios Pomonis <pomonis@google.com>
Reviewed-by: Andrew Honig <ahonig@google.com>
Cc: stable@vger.kernel.org
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Marios Pomonis 2019-12-11 12:47:47 -08:00 committed by Paolo Bonzini
parent 4bf79cb089
commit 25a5edea71
1 changed files with 6 additions and 2 deletions
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8
arch/x86/kvm/mtrr.c
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@ -192,11 +192,15 @@ static bool fixed_msr_to_seg_unit(u32 msr, int *seg, int *unit)
break;
case MSR_MTRRfix16K_80000 ... MSR_MTRRfix16K_A0000:
*seg = 1;
*unit = msr - MSR_MTRRfix16K_80000;
*unit = array_index_nospec(
msr - MSR_MTRRfix16K_80000,
MSR_MTRRfix16K_A0000 - MSR_MTRRfix16K_80000 + 1);
break;
case MSR_MTRRfix4K_C0000 ... MSR_MTRRfix4K_F8000:
*seg = 2;
*unit = msr - MSR_MTRRfix4K_C0000;
*unit = array_index_nospec(
msr - MSR_MTRRfix4K_C0000,
MSR_MTRRfix4K_F8000 - MSR_MTRRfix4K_C0000 + 1);
break;
default:
return false;