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Commit 6c475352 authored by Marcelo Tosatti's avatar Marcelo Tosatti Committed by Avi Kivity
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KVM: MMU: avoid creation of unreachable pages in the shadow 



It is possible for a shadow page to have a parent link
pointing to a freed page. When zapping a high level table,
kvm_mmu_page_unlink_children fails to remove the parent_pte link.
For that to happen, the child must be unreachable via the shadow
tree, which can happen in shadow_walk_entry if the guest pte was
modified in between walk() and fetch(). Remove the parent pte
reference in such case.

Possible cause for oops in bug #2217430.

Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent c30f8a6c

arch/x86/kvm/paging_tmpl.h

+1 −0
Original line number Diff line number Diff line
@@ -331,6 +331,7 @@ static int FNAME(shadow_walk_entry)(struct kvm_shadow_walk *_sw, 
		r = kvm_read_guest_atomic(vcpu->kvm, gw->pte_gpa[level - 2],

					  &curr_pte, sizeof(curr_pte));

		if (r || curr_pte != gw->ptes[level - 2]) {

			kvm_mmu_put_page(shadow_page, sptep);

			kvm_release_pfn_clean(sw->pfn);

			sw->sptep = NULL;

			return 1;