Commit 03617c18 authored by Gleb Natapov's avatar Gleb Natapov Committed by Paolo Bonzini

KVM: VMX: mark unusable segment as nonpresent

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.

Cc: stable@vger.kernel.org # 3.9+
Reported-by: default avatarStefan Pietsch <stefan.pietsch@lsexperts.de>
Tested-by: default avatarStefan Pietsch <stefan.pietsch@lsexperts.de>
Signed-off-by: default avatarGleb Natapov <gleb@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent c3eb5b14
...@@ -3404,15 +3404,22 @@ static void vmx_get_segment(struct kvm_vcpu *vcpu, ...@@ -3404,15 +3404,22 @@ static void vmx_get_segment(struct kvm_vcpu *vcpu,
var->limit = vmx_read_guest_seg_limit(vmx, seg); var->limit = vmx_read_guest_seg_limit(vmx, seg);
var->selector = vmx_read_guest_seg_selector(vmx, seg); var->selector = vmx_read_guest_seg_selector(vmx, seg);
ar = vmx_read_guest_seg_ar(vmx, seg); ar = vmx_read_guest_seg_ar(vmx, seg);
var->unusable = (ar >> 16) & 1;
var->type = ar & 15; var->type = ar & 15;
var->s = (ar >> 4) & 1; var->s = (ar >> 4) & 1;
var->dpl = (ar >> 5) & 3; 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->avl = (ar >> 12) & 1;
var->l = (ar >> 13) & 1; var->l = (ar >> 13) & 1;
var->db = (ar >> 14) & 1; var->db = (ar >> 14) & 1;
var->g = (ar >> 15) & 1; var->g = (ar >> 15) & 1;
var->unusable = (ar >> 16) & 1;
} }
static u64 vmx_get_segment_base(struct kvm_vcpu *vcpu, int seg) static u64 vmx_get_segment_base(struct kvm_vcpu *vcpu, int seg)
......
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