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Reply-To: Sean Christopherson <seanjc@google.com>
Date:   Thu,  4 Mar 2021 17:10:51 -0800
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Subject: [PATCH v2 07/17] KVM: x86/mmu: Check PDPTRs before allocating PAE roots
From:   Sean Christopherson <seanjc@google.com>
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     Sean Christopherson <seanjc@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, Ben Gardon <bgardon@google.com>,
        Brijesh Singh <brijesh.singh@amd.com>,
        Tom Lendacky <thomas.lendacky@amd.com>
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Precedence: bulk

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 <seanjc@google.com>
---
 arch/x86/kvm/mmu/mmu.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 7ebfbc77b050..9fc2b46f8541 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3269,7 +3269,7 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
 static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
 {
 	struct kvm_mmu *mmu = vcpu->arch.mmu;
-	u64 pdptr, pm_mask;
+	u64 pdptrs[4], pm_mask;
 	gfn_t root_gfn, root_pgd;
 	hpa_t root;
 	int i;
@@ -3280,6 +3280,17 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
 	if (mmu_check_root(vcpu, root_gfn))
 		return 1;
 
+	if (mmu->root_level == PT32E_ROOT_LEVEL) {
+		for (i = 0; i < 4; ++i) {
+			pdptrs[i] = 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.
@@ -3309,14 +3320,11 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
 		MMU_WARN_ON(VALID_PAGE(mmu->pae_root[i]));
 
 		if (mmu->root_level == PT32E_ROOT_LEVEL) {
-			pdptr = mmu->get_pdptr(vcpu, i);
-			if (!(pdptr & PT_PRESENT_MASK)) {
+			if (!(pdptrs[i] & PT_PRESENT_MASK)) {
 				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,
-- 
2.30.1.766.gb4fecdf3b7-goog