This is a note to let you know that I've just added the patch titled
KVM: VMX: mark unusable segment as nonpresent
to the 3.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-vmx-mark-unusable-segment-as-nonpresent.patch
and it can be found in the queue-3.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 03617c188f41eeeb4223c919ee7e66e5a114f2c6 Mon Sep 17 00:00:00 2001
From: Gleb Natapov <gleb@xxxxxxxxxx>
Date: Fri, 28 Jun 2013 13:17:18 +0300
Subject: KVM: VMX: mark unusable segment as nonpresent
From: Gleb Natapov <gleb@xxxxxxxxxx>
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@xxxxxxxxxxxx>
Tested-by: Stefan Pietsch <stefan.pietsch@xxxxxxxxxxxx>
Signed-off-by: Gleb Natapov <gleb@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/vmx.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3259,15 +3259,22 @@ static void vmx_get_segment(struct kvm_v
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)
Patches currently in stable-queue which might be from gleb@xxxxxxxxxx are
queue-3.9/kvm-vmx-mark-unusable-segment-as-nonpresent.patch
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