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>

1 files changed, 3 insertions, 1 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e00dd0515a84..b9f55299ed7e 100644
--- 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;