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[2/9] KVM: x86: Check CR3 GPA for validity regardless of vCPU mode

Message ID 20210213010518.1682691-3-seanjc@google.com (mailing list archive)
State New, archived
Headers show
Series KVM: x86: Fixes for (benign?) truncation bugs | expand

Commit Message

Sean Christopherson Feb. 13, 2021, 1:05 a.m. UTC 
Check CR3 for an invalid GPA even if the vCPU isn't in long mode.  For
bigger emulation flows, notably RSM, the vCPU mode may not be accurate
if CR0/CR4 are loaded after CR3.  For MOV CR3 and similar flows, the
caller is responsible for truncating the value.

Note, SMRAM.CR3 is read-only, so this is mostly a theoretical bug since
KVM will not have stored an illegal CR3 into SMRAM during SMI emulation.

Fixes: 660a5d517aaa ("KVM: x86: save/load state on SMM switch")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/x86.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3fa140383f5d..72fd8d384df7 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1073,10 +1073,15 @@  int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
 		return 0;
 	}
 
-	if (is_long_mode(vcpu) && kvm_vcpu_is_illegal_gpa(vcpu, cr3))
+	/*
+	 * Do not condition the GPA check on long mode, this helper is used to
+	 * stuff CR3, e.g. for RSM emulation, and there is no guarantee that
+	 * the current vCPU mode is accurate.
+	 */
+	if (kvm_vcpu_is_illegal_gpa(vcpu, cr3))
 		return 1;
-	else if (is_pae_paging(vcpu) &&
-		 !load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3))
+
+	if (is_pae_paging(vcpu) && !load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3))
 		return 1;
 
 	kvm_mmu_new_pgd(vcpu, cr3, skip_tlb_flush, skip_tlb_flush);