KVM: x86 emulator: If LOCK prefix is used dest arg should be memory.

If LOCK prefix is used dest arg should be memory, otherwise instruction
should generate #UD.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index b89a8f217332..46a7ee3040a0 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1842,7 +1842,7 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
         }
 
         /* LOCK prefix is allowed only with some instructions */
-        if (c->lock_prefix && !(c->d & Lock)) {
+        if (c->lock_prefix && (!(c->d & Lock) || c->dst.type != OP_MEM)) {
                 kvm_queue_exception(ctxt->vcpu, UD_VECTOR);
                 goto done;
         }