KVM: VMX: Fix %ds/%es clobber

The vmx exit code unconditionally restores %ds and %es to __USER_DS.  This
can override the user's values, since %ds and %es are not saved and restored
in x86_64 syscalls.  In practice, this isn't dangerous since nobody uses
segment registers in long mode, least of all programs that use KVM.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 3062ea95266..f2ee016e100 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6102,7 +6102,10 @@ static void atomic_switch_perf_msrs(struct vcpu_vmx *vmx)
 static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
 {
         struct vcpu_vmx *vmx = to_vmx(vcpu);
+        u16 _ds, _es;
 
+        savesegment(ds, _ds);
+        savesegment(es, _es);
         if (is_guest_mode(vcpu) && !vmx->nested.nested_run_pending) {
                 struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
                 if (vmcs12->idt_vectoring_info_field &
@@ -6263,7 +6266,8 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
                 }
         }
 
-        asm("mov %0, %%ds; mov %0, %%es" : : "r"(__USER_DS));
+        loadsegment(ds, _ds);
+        loadsegment(es, _es);
         vmx->loaded_vmcs->launched = 1;
 
         vmx->exit_reason = vmcs_read32(VM_EXIT_REASON);