KVM: x86: fix use of uninitialized memory as segment descriptor in emulator.

If VMX reports segment as unusable, zero descriptor passed by the emulator
before returning. Such descriptor will be considered not present by the
emulator.

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

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e00dd0515a84874af7b55fd1a5f828180d721ee3..b9f55299ed7e1ac535f8236626c4d5642f4c093b 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4489,8 +4489,10 @@ static bool emulator_get_segment(struct x86_emulate_ctxt *ctxt, u16 *selector,
        kvm_get_segment(emul_to_vcpu(ctxt), &var, seg);
        *selector = var.selector;
 
-       if (var.unusable)
+       if (var.unusable) {
+               memset(desc, 0, sizeof(*desc));
                return false;
+       }
 
        if (var.g)
                var.limit >>= 12;