Add lockdep assertions in get_vmcs12() and get_shadow_vmcs12() to verify the vCPU's mutex is held, as the returned VMCS objects are dynamically allocated/freed when nested VMX is turned on/off, i.e. accessing vmcs12 structures without holding vcpu->mutex is susceptible to use-after-free. Waive the assertion if the VM is being destroyed, as KVM currently forces a nested VM-Exit when freeing the vCPU. If/when that wart is fixed, the assertion can/should be converted to an unqualified lockdep assertion. See also https://lore.kernel.org/all/Zsd0TqCeY3B5Sb5b@xxxxxxxxxx. Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> --- arch/x86/kvm/vmx/nested.h | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/arch/x86/kvm/vmx/nested.h b/arch/x86/kvm/vmx/nested.h index cce4e2aa30fb..668b6c83a373 100644 --- a/arch/x86/kvm/vmx/nested.h +++ b/arch/x86/kvm/vmx/nested.h @@ -39,11 +39,17 @@ bool nested_vmx_check_io_bitmaps(struct kvm_vcpu *vcpu, unsigned int port, static inline struct vmcs12 *get_vmcs12(struct kvm_vcpu *vcpu) { + lockdep_assert_once(lockdep_is_held(&vcpu->mutex) || + !refcount_read(&vcpu->kvm->users_count)); + return to_vmx(vcpu)->nested.cached_vmcs12; } static inline struct vmcs12 *get_shadow_vmcs12(struct kvm_vcpu *vcpu) { + lockdep_assert_once(lockdep_is_held(&vcpu->mutex) || + !refcount_read(&vcpu->kvm->users_count)); + return to_vmx(vcpu)->nested.cached_shadow_vmcs12; } -- 2.46.0.469.g59c65b2a67-goog
