Commit 25a5edea authored by Marios Pomonis's avatar Marios Pomonis Committed by Paolo Bonzini
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KVM: x86: Protect MSR-based index computations in fixed_msr_to_seg_unit() from... 


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

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: de9aef5e ("KVM: MTRR: introduce fixed_mtrr_segment table")

Signed-off-by: default avatarNick Finco <nifi@google.com>
Signed-off-by: default avatarMarios Pomonis <pomonis@google.com>
Reviewed-by: default avatarAndrew Honig <ahonig@google.com>
Cc: stable@vger.kernel.org
Reviewed-by: default avatarJim Mattson <jmattson@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 4bf79cb0

arch/x86/kvm/mtrr.c

+6 −2
Original line number Diff line number Diff line
@@ -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;