KVM: nVMX: Unconditionally uninit the MMU on nested vmexit

Three reasons for doing this: 1. arch.walk_mmu points to arch.mmu anyway
in case nested EPT wasn't in use. 2. this aligns VMX with SVM. But 3. is
most important: nested_cpu_has_ept(vmcs12) queries the VMCS page, and if
one guest VCPU manipulates the page of another VCPU in L2, we may be
fooled to skip over the nested_ept_uninit_mmu_context, leaving mmu in
nested state. That can crash the host later on if nested_ept_get_cr3 is
invoked while L1 already left vmxon and nested.current_vmcs12 became
NULL therefore.

Cc: stable@kernel.org
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index b2fe1c252f35f92e3b6707406998738a9275c8d2..da7837e1349da8ac4ac06468fb2f05e798e136f1 100644 (file)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -8283,8 +8283,7 @@ static void load_vmcs12_host_state(struct kvm_vcpu *vcpu,
        vcpu->arch.cr4_guest_owned_bits = ~vmcs_readl(CR4_GUEST_HOST_MASK);
        kvm_set_cr4(vcpu, vmcs12->host_cr4);
 
-       if (nested_cpu_has_ept(vmcs12))
-               nested_ept_uninit_mmu_context(vcpu);
+       nested_ept_uninit_mmu_context(vcpu);
 
        kvm_set_cr3(vcpu, vmcs12->host_cr3);
        kvm_mmu_reset_context(vcpu);