Commit 25a5edea authored Dec 11, 2019 by Marios Pomonis Committed by Paolo Bonzini Jan 27, 2020

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: 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>

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;

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