From 9e7b0e7fba45ca3c6357aeb7091ebc281f1de365 Mon Sep 17 00:00:00 2001 From: Xiao Guangrong Date: Wed, 30 Jun 2010 16:03:28 +0800 Subject: [PATCH] KVM: MMU: fix direct sp's access corrupted If the mapping is writable but the dirty flag is not set, we will find the read-only direct sp and setup the mapping, then if the write #PF occur, we will mark this mapping writable in the read-only direct sp, now, other real read-only mapping will happily write it without #PF. It may hurt guest's COW Fixed by re-install the mapping when write #PF occur. Signed-off-by: Xiao Guangrong Signed-off-by: Marcelo Tosatti --- arch/x86/kvm/paging_tmpl.h | 28 ++++++++++++++++++++++++++-- 1 file changed, 26 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h index f4e4aaa65ff..117d63f6304 100644 --- a/arch/x86/kvm/paging_tmpl.h +++ b/arch/x86/kvm/paging_tmpl.h @@ -325,8 +325,32 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr, break; } - if (is_shadow_present_pte(*sptep) && !is_large_pte(*sptep)) - continue; + if (is_shadow_present_pte(*sptep) && !is_large_pte(*sptep)) { + struct kvm_mmu_page *child; + unsigned direct_access; + + if (level != gw->level) + continue; + + /* + * For the direct sp, if the guest pte's dirty bit + * changed form clean to dirty, it will corrupt the + * sp's access: allow writable in the read-only sp, + * so we should update the spte at this point to get + * a new sp with the correct access. + */ + direct_access = gw->pt_access & gw->pte_access; + if (!is_dirty_gpte(gw->ptes[gw->level - 1])) + direct_access &= ~ACC_WRITE_MASK; + + child = page_header(*sptep & PT64_BASE_ADDR_MASK); + if (child->role.access == direct_access) + continue; + + mmu_page_remove_parent_pte(child, sptep); + __set_spte(sptep, shadow_trap_nonpresent_pte); + kvm_flush_remote_tlbs(vcpu->kvm); + } if (is_large_pte(*sptep)) { rmap_remove(vcpu->kvm, sptep); -- 2.20.1