diff mbox series

[4.4,43/91] KVM: x86: Protect MSR-based index computations in fixed_msr_to_seg_unit() from Spectre-v1/L1TF attacks

Message ID 20200213151838.314721719@linuxfoundation.org
State Superseded
Headers show
Series None | expand

Commit Message

Greg Kroah-Hartman Feb. 13, 2020, 3:20 p.m. UTC 
From: Marios Pomonis <pomonis@google.com>

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@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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/kvm/mtrr.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)
diff mbox series

Patch

--- a/arch/x86/kvm/mtrr.c
+++ b/arch/x86/kvm/mtrr.c
@@ -17,6 +17,7 @@ 
  */
 
 #include <linux/kvm_host.h>
+#include <linux/nospec.h>
 #include <asm/mtrr.h>
 
 #include "cpuid.h"
@@ -202,11 +203,15 @@  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;