KVM: x86: check for cr3 validity in mmu_alloc_roots

Verify the cr3 address stored in vcpu->arch.cr3 points to an existant
memslot. If not, inject a triple fault.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 23 insertions, 4 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 3ce60ad1fe37..5c3d6e81a7dc 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1912,7 +1912,19 @@ static void mmu_free_roots(struct kvm_vcpu *vcpu)
         vcpu->arch.mmu.root_hpa = INVALID_PAGE;
 }
 
-static void mmu_alloc_roots(struct kvm_vcpu *vcpu)
+static int mmu_check_root(struct kvm_vcpu *vcpu, gfn_t root_gfn)
+{
+        int ret = 0;
+
+        if (!kvm_is_visible_gfn(vcpu->kvm, root_gfn)) {
+                set_bit(KVM_REQ_TRIPLE_FAULT, &vcpu->requests);
+                ret = 1;
+        }
+
+        return ret;
+}
+
+static int mmu_alloc_roots(struct kvm_vcpu *vcpu)
 {
         int i;
         gfn_t root_gfn;
@@ -1927,13 +1939,15 @@ static void mmu_alloc_roots(struct kvm_vcpu *vcpu)
                 ASSERT(!VALID_PAGE(root));
                 if (tdp_enabled)
                         direct = 1;
+                if (mmu_check_root(vcpu, root_gfn))
+                        return 1;
                 sp = kvm_mmu_get_page(vcpu, root_gfn, 0,
                                       PT64_ROOT_LEVEL, direct,
                                       ACC_ALL, NULL);
                 root = __pa(sp->spt);
                 ++sp->root_count;
                 vcpu->arch.mmu.root_hpa = root;
-                return;
+                return 0;
         }
         direct = !is_paging(vcpu);
         if (tdp_enabled)
@@ -1950,6 +1964,8 @@ static void mmu_alloc_roots(struct kvm_vcpu *vcpu)
                         root_gfn = vcpu->arch.pdptrs[i] >> PAGE_SHIFT;
                 } else if (vcpu->arch.mmu.root_level == 0)
                         root_gfn = 0;
+                if (mmu_check_root(vcpu, root_gfn))
+                        return 1;
                 sp = kvm_mmu_get_page(vcpu, root_gfn, i << 30,
                                       PT32_ROOT_LEVEL, direct,
                                       ACC_ALL, NULL);
@@ -1958,6 +1974,7 @@ static void mmu_alloc_roots(struct kvm_vcpu *vcpu)
                 vcpu->arch.mmu.pae_root[i] = root | PT_PRESENT_MASK;
         }
         vcpu->arch.mmu.root_hpa = __pa(vcpu->arch.mmu.pae_root);
+        return 0;
 }
 
 static void mmu_sync_roots(struct kvm_vcpu *vcpu)
@@ -1976,7 +1993,7 @@ static void mmu_sync_roots(struct kvm_vcpu *vcpu)
         for (i = 0; i < 4; ++i) {
                 hpa_t root = vcpu->arch.mmu.pae_root[i];
 
-                if (root) {
+                if (root && VALID_PAGE(root)) {
                         root &= PT64_BASE_ADDR_MASK;
                         sp = page_header(root);
                         mmu_sync_children(vcpu, sp);
@@ -2311,9 +2328,11 @@ int kvm_mmu_load(struct kvm_vcpu *vcpu)
                 goto out;
         spin_lock(&vcpu->kvm->mmu_lock);
         kvm_mmu_free_some_pages(vcpu);
-        mmu_alloc_roots(vcpu);
+        r = mmu_alloc_roots(vcpu);
         mmu_sync_roots(vcpu);
         spin_unlock(&vcpu->kvm->mmu_lock);
+        if (r)
+                goto out;
         kvm_x86_ops->set_cr3(vcpu, vcpu->arch.mmu.root_hpa);
         kvm_mmu_flush_tlb(vcpu);
 out: