KVM: x86 emulator: Forbid modifying CS segment register by mov instruction
Inject #UD if guest attempts to do so. This is in accordance to Intel
SDM.
Cc: stable@kernel.org (2.6.33, 2.6.32)
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index c280c23..2db760f 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2126,6 +2126,12 @@
int err;
sel = c->src.val;
+
+ if (c->modrm_reg == VCPU_SREG_CS) {
+ kvm_queue_exception(ctxt->vcpu, UD_VECTOR);
+ goto done;
+ }
+
if (c->modrm_reg == VCPU_SREG_SS)
toggle_interruptibility(ctxt, X86_SHADOW_INT_MOV_SS);