KVM: fix EFER read buffer overflow

Check whether index is within bounds before grabbing the element.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Cc: Avi Kivity <avi@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 0ba706e87c50..31c3a8740c42 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -571,12 +571,15 @@ static void reload_tss(void)
 static void load_transition_efer(struct vcpu_vmx *vmx)
 {
         int efer_offset = vmx->msr_offset_efer;
-        u64 host_efer = vmx->host_msrs[efer_offset].data;
-        u64 guest_efer = vmx->guest_msrs[efer_offset].data;
+        u64 host_efer;
+        u64 guest_efer;
         u64 ignore_bits;
 
         if (efer_offset < 0)
                 return;
+        host_efer = vmx->host_msrs[efer_offset].data;
+        guest_efer = vmx->guest_msrs[efer_offset].data;
+
         /*
          * NX is emulated; LMA and LME handled by hardware; SCE meaninless
          * outside long mode