Patch-mainline: v5.6-rc1

Git-commit: 25a5edea71b7c154b6a0b8cec14c711cafa31d26

From: Marios Pomonis <pomonis@google.com>

Date: Wed, 11 Dec 2019 12:47:47 -0800

Subject: [PATCH] KVM: x86: Protect MSR-based index computations in

 fixed_msr_to_seg_unit() from Spectre-v1/L1TF attacks

References: bsc#1164731

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@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>

Signed-off-by: Juergen Gross <jgross@suse.com>

---

 arch/x86/kvm/mtrr.c | 8 ++++++--

 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mtrr.c b/arch/x86/kvm/mtrr.c

index 25ce3edd1872..7f0059aa30e1 100644

--- a/arch/x86/kvm/mtrr.c

+++ b/arch/x86/kvm/mtrr.c

@@ -202,11 +202,15 @@ 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;

-- 

2.16.4