From: Marios Pomonis <pomonis@xxxxxxxxxx> commit 25a5edea71b7c154b6a0b8cec14c711cafa31d26 upstream. 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: de9aef5e1ad6 ("KVM: MTRR: introduce fixed_mtrr_segment table") Signed-off-by: Nick Finco <nifi@xxxxxxxxxx> Signed-off-by: Marios Pomonis <pomonis@xxxxxxxxxx> Reviewed-by: Andrew Honig <ahonig@xxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Reviewed-by: Jim Mattson <jmattson@xxxxxxxxxx> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/kvm/mtrr.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) --- a/arch/x86/kvm/mtrr.c +++ b/arch/x86/kvm/mtrr.c @@ -202,11 +202,15 @@ static bool fixed_msr_to_seg_unit(u32 ms 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;