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@xxxxxxxxxx>
---
arch/x86/kvm/vmx.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 61ebdb6..16edeea 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);
--
1.7.10.1
--
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