Commit 76447864 authored Aug 30, 2022 by Sean Christopherson Committed by Greg Kroah-Hartman Oct 26, 2022

KVM: nVMX: Unconditionally purge queued/injected events on nested "exit"



commit d953540430c5af57f5de97ea9e36253908204027 upstream.

Drop pending exceptions and events queued for re-injection when leaving
nested guest mode, even if the "exit" is due to VM-Fail, SMI, or forced
by host userspace.  Failure to purge events could result in an event
belonging to L2 being injected into L1.

This _should_ never happen for VM-Fail as all events should be blocked by
nested_run_pending, but it's possible if KVM, not the L1 hypervisor, is
the source of VM-Fail when running vmcs02.

SMI is a nop (barring unknown bugs) as recognition of SMI and thus entry
to SMM is blocked by pending exceptions and re-injected events.

Forced exit is definitely buggy, but has likely gone unnoticed because
userspace probably follows the forced exit with KVM_SET_VCPU_EVENTS (or
some other ioctl() that purges the queue).

Fixes: 4f350c6d ("kvm: nVMX: Handle deferred early VMLAUNCH/VMRESUME failure properly")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20220830231614.3580124-2-seanjc@google.com


Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 45779be5

arch/x86/kvm/vmx/nested.c

+11 −8

Original line number	Diff line number	Diff line
		@@ -3762,14 +3762,6 @@ static void prepare_vmcs12(struct kvm_vcpu vcpu, struct vmcs12 vmcs12,
		nested_vmx_abort(vcpu,
		VMX_ABORT_SAVE_GUEST_MSR_FAIL);
		}

		/*
		* Drop what we picked up for L2 via vmx_complete_interrupts. It is
		* preserved above and would only end up incorrectly in L1.
		*/
		vcpu->arch.nmi_injected = false;
		kvm_clear_exception_queue(vcpu);
		kvm_clear_interrupt_queue(vcpu);
		}

		/*
		@@ -4104,6 +4096,17 @@ void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason,
		WARN_ON_ONCE(nested_early_check);
		}

		/*
		* Drop events/exceptions that were queued for re-injection to L2
		* (picked up via vmx_complete_interrupts()), as well as exceptions
		* that were pending for L2. Note, this must NOT be hoisted above
		* prepare_vmcs12(), events/exceptions queued for re-injection need to
		* be captured in vmcs12 (see vmcs12_save_pending_event()).
		*/
		vcpu->arch.nmi_injected = false;
		kvm_clear_exception_queue(vcpu);
		kvm_clear_interrupt_queue(vcpu);

		vmx_switch_vmcs(vcpu, &vmx->vmcs01);

		/* Update any VMCS fields that might have changed while L2 ran */