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authorGleb Natapov <gleb@redhat.com>2013-06-28 13:17:18 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-07-13 11:42:27 -0700
commit096bff23937209645162a7fc5e70246cb5c60336 (patch)
tree1c189e4d521275757a77112945e950b5a7f7e18c
parentc334daca734bbb11f79742ec699b1cf9d2112117 (diff)
KVM: VMX: mark unusable segment as nonpresent
commit 03617c188f41eeeb4223c919ee7e66e5a114f2c6 upstream. Some userspaces do not preserve unusable property. Since usable segment has to be present according to VMX spec we can use present property to amend userspace bug by making unusable segment always nonpresent. vmx_segment_access_rights() already marks nonpresent segment as unusable. Reported-by: Stefan Pietsch <stefan.pietsch@lsexperts.de> Tested-by: Stefan Pietsch <stefan.pietsch@lsexperts.de> Signed-off-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/x86/kvm/vmx.c11
1 files changed, 9 insertions, 2 deletions
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 260a9193955..5402c94ab76 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3399,15 +3399,22 @@ static void vmx_get_segment(struct kvm_vcpu *vcpu,
var->limit = vmx_read_guest_seg_limit(vmx, seg);
var->selector = vmx_read_guest_seg_selector(vmx, seg);
ar = vmx_read_guest_seg_ar(vmx, seg);
+ var->unusable = (ar >> 16) & 1;
var->type = ar & 15;
var->s = (ar >> 4) & 1;
var->dpl = (ar >> 5) & 3;
- var->present = (ar >> 7) & 1;
+ /*
+ * Some userspaces do not preserve unusable property. Since usable
+ * segment has to be present according to VMX spec we can use present
+ * property to amend userspace bug by making unusable segment always
+ * nonpresent. vmx_segment_access_rights() already marks nonpresent
+ * segment as unusable.
+ */
+ var->present = !var->unusable;
var->avl = (ar >> 12) & 1;
var->l = (ar >> 13) & 1;
var->db = (ar >> 14) & 1;
var->g = (ar >> 15) & 1;
- var->unusable = (ar >> 16) & 1;
}
static u64 vmx_get_segment_base(struct kvm_vcpu *vcpu, int seg)