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KVM: VMX: Fix %ds/%es clobber

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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>
This commit is contained in:
Avi Kivity 2012-05-13 19:53:23 +03:00 committed by Marcelo Tosatti
parent d54e4237bc
commit 512d5649e8
1 changed files with 5 additions and 1 deletions
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6
arch/x86/kvm/vmx.c
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@ -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);