From 6c475352e87224a8f0b8cc6f6cc96b30563dc5b4 Mon Sep 17 00:00:00 2001 From: Marcelo Tosatti Date: Tue, 25 Nov 2008 15:33:10 +0100 Subject: [PATCH] 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: Marcelo Tosatti Signed-off-by: Avi Kivity --- arch/x86/kvm/paging_tmpl.h | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h index 613ec9aa674a..84eee43bbe74 100644 --- a/arch/x86/kvm/paging_tmpl.h +++ b/arch/x86/kvm/paging_tmpl.h @@ -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; -- GitLab