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Subject[PATCH 43/54] KVM: MMU: Set nx bit correctly on shadow ptes
Date
While the page table walker correctly generates a guest page fault
if a guest tries to execute a non-executable page, the shadow code does
not mark it non-executable. This means that if a guest accesses an nx
page first with a read access, then subsequent code fetch accesses will
succeed.

Fix by setting the nx bit on shadow ptes.

Signed-off-by: Avi Kivity <avi@qumranet.com>
---
drivers/kvm/paging_tmpl.h | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/drivers/kvm/paging_tmpl.h b/drivers/kvm/paging_tmpl.h
index 7688cbf..59ba752 100644
--- a/drivers/kvm/paging_tmpl.h
+++ b/drivers/kvm/paging_tmpl.h
@@ -255,6 +255,8 @@ static void FNAME(set_pte)(struct kvm_vcpu *vcpu, pt_element_t gpte,
spte |= gpte & PT64_NX_MASK;
if (!dirty)
pte_access &= ~ACC_WRITE_MASK;
+ if (!(pte_access & ACC_EXEC_MASK))
+ spte |= PT64_NX_MASK;

page = gfn_to_page(vcpu->kvm, gfn);

--
1.5.3.7


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