Commit 29bf08f1 authored Dec 28, 2013 by Jan Kiszka Committed by Marcelo Tosatti Jan 02, 2014

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>

parent e66d2ae7

arch/x86/kvm/vmx.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -8283,7 +8283,6 @@ 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);

		kvm_set_cr3(vcpu, vmcs12->host_cr3);

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