[05/15] KVM: x86/mmu: Check PDPTRs before allocating PAE roots

Commit Message

Sean Christopherson March 2, 2021, 6:45 p.m. UTC

Check the validity of the PDPTRs before allocating any of the PAE roots,
otherwise a bad PDPTR will cause KVM to leak any previously allocated
roots.

Signed-off-by: Sean Christopherson <[e-mail]>
---
 arch/x86/kvm/mmu/mmu.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

Patch

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index e5c3701112f8..aa20e8d32197 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3262,7 +3262,7 @@  static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
 
 static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
 {
-	u64 pdptr, pm_mask;
+	u64 pdptrs[4], pm_mask;
 	gfn_t root_gfn, root_pgd;
 	hpa_t root;
 	int i;
@@ -3273,6 +3273,17 @@  static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
 	if (mmu_check_root(vcpu, root_gfn))
 		return 1;
 
+	if (vcpu->arch.mmu->root_level == PT32E_ROOT_LEVEL) {
+		for (i = 0; i < 4; ++i) {
+			pdptrs[i] = vcpu->arch.mmu->get_pdptr(vcpu, i);
+			if (!(pdptrs[i] & PT_PRESENT_MASK))
+				continue;
+
+			if (mmu_check_root(vcpu, pdptrs[i] >> PAGE_SHIFT))
+				return 1;
+		}
+	}
+
 	/*
 	 * Do we shadow a long mode page table? If so we need to
 	 * write-protect the guests page table root.
@@ -3331,14 +3342,11 @@  static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
 		MMU_WARN_ON(VALID_PAGE(vcpu->arch.mmu->pae_root[i]));
 
 		if (vcpu->arch.mmu->root_level == PT32E_ROOT_LEVEL) {
-			pdptr = vcpu->arch.mmu->get_pdptr(vcpu, i);
-			if (!(pdptr & PT_PRESENT_MASK)) {
+			if (!(pdptrs[i] & PT_PRESENT_MASK)) {
 				vcpu->arch.mmu->pae_root[i] = 0;
 				continue;
 			}
-			root_gfn = pdptr >> PAGE_SHIFT;
-			if (mmu_check_root(vcpu, root_gfn))
-				return 1;
+			root_gfn = pdptrs[i] >> PAGE_SHIFT;
 		}
 
 		root = mmu_alloc_root(vcpu, root_gfn, i << 30,