KVM: VMX: Avoid leaking fake realmode state to userspace
When emulating real mode, we fake some state:
- tr.base points to a fake vm86 tss
- segment registers are made to conform to vm86 restrictions
change vmx_get_segment() not to expose this fake state to userspace;
instead, return the original state.
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index a2e83a9..87ad551 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2032,23 +2032,40 @@
vmcs_writel(GUEST_CR4, hw_cr4);
}
-static u64 vmx_get_segment_base(struct kvm_vcpu *vcpu, int seg)
-{
- struct kvm_vmx_segment_field *sf = &kvm_vmx_segment_fields[seg];
-
- return vmcs_readl(sf->base);
-}
-
static void vmx_get_segment(struct kvm_vcpu *vcpu,
struct kvm_segment *var, int seg)
{
+ struct vcpu_vmx *vmx = to_vmx(vcpu);
struct kvm_vmx_segment_field *sf = &kvm_vmx_segment_fields[seg];
+ struct kvm_save_segment *save;
u32 ar;
+ if (vmx->rmode.vm86_active
+ && (seg == VCPU_SREG_TR || seg == VCPU_SREG_ES
+ || seg == VCPU_SREG_DS || seg == VCPU_SREG_FS
+ || seg == VCPU_SREG_GS)
+ && !emulate_invalid_guest_state) {
+ switch (seg) {
+ case VCPU_SREG_TR: save = &vmx->rmode.tr; break;
+ case VCPU_SREG_ES: save = &vmx->rmode.es; break;
+ case VCPU_SREG_DS: save = &vmx->rmode.ds; break;
+ case VCPU_SREG_FS: save = &vmx->rmode.fs; break;
+ case VCPU_SREG_GS: save = &vmx->rmode.gs; break;
+ default: BUG();
+ }
+ var->selector = save->selector;
+ var->base = save->base;
+ var->limit = save->limit;
+ ar = save->ar;
+ if (seg == VCPU_SREG_TR
+ || var->selector == vmcs_read16(sf->selector))
+ goto use_saved_rmode_seg;
+ }
var->base = vmcs_readl(sf->base);
var->limit = vmcs_read32(sf->limit);
var->selector = vmcs_read16(sf->selector);
ar = vmcs_read32(sf->ar_bytes);
+use_saved_rmode_seg:
if ((ar & AR_UNUSABLE_MASK) && !emulate_invalid_guest_state)
ar = 0;
var->type = ar & 15;
@@ -2062,6 +2079,18 @@
var->unusable = (ar >> 16) & 1;
}
+static u64 vmx_get_segment_base(struct kvm_vcpu *vcpu, int seg)
+{
+ struct kvm_vmx_segment_field *sf = &kvm_vmx_segment_fields[seg];
+ struct kvm_segment s;
+
+ if (to_vmx(vcpu)->rmode.vm86_active) {
+ vmx_get_segment(vcpu, &s, seg);
+ return s.base;
+ }
+ return vmcs_readl(sf->base);
+}
+
static int vmx_get_cpl(struct kvm_vcpu *vcpu)
{
if (!is_protmode(vcpu))