KVM: x86: Protect exit_reason from being used in Spectre-v1/L1TF attacks
This fixes a Spectre-v1/L1TF vulnerability in vmx_handle_exit().
While exit_reason is set by the hardware and therefore should not be
attacker-influenced, an unknown exit_reason could potentially be used to
perform such an attack.
Fixes: 55d2375e58a6 ("KVM: nVMX: Move nested code to dedicated files")
Signed-off-by: Marios Pomonis <pomonis@google.com>
Signed-off-by: Nick Finco <nifi@google.com>
Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Andrew Honig <ahonig@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 5415cd4..62fb639 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5913,34 +5913,41 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu,
if (exit_fastpath == EXIT_FASTPATH_SKIP_EMUL_INS) {
kvm_skip_emulated_instruction(vcpu);
return 1;
- } else if (exit_reason < kvm_vmx_max_exit_handlers
- && kvm_vmx_exit_handlers[exit_reason]) {
-#ifdef CONFIG_RETPOLINE
- if (exit_reason == EXIT_REASON_MSR_WRITE)
- return kvm_emulate_wrmsr(vcpu);
- else if (exit_reason == EXIT_REASON_PREEMPTION_TIMER)
- return handle_preemption_timer(vcpu);
- else if (exit_reason == EXIT_REASON_INTERRUPT_WINDOW)
- return handle_interrupt_window(vcpu);
- else if (exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT)
- return handle_external_interrupt(vcpu);
- else if (exit_reason == EXIT_REASON_HLT)
- return kvm_emulate_halt(vcpu);
- else if (exit_reason == EXIT_REASON_EPT_MISCONFIG)
- return handle_ept_misconfig(vcpu);
-#endif
- return kvm_vmx_exit_handlers[exit_reason](vcpu);
- } else {
- vcpu_unimpl(vcpu, "vmx: unexpected exit reason 0x%x\n",
- exit_reason);
- dump_vmcs();
- vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
- vcpu->run->internal.suberror =
- KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON;
- vcpu->run->internal.ndata = 1;
- vcpu->run->internal.data[0] = exit_reason;
- return 0;
}
+
+ if (exit_reason >= kvm_vmx_max_exit_handlers)
+ goto unexpected_vmexit;
+#ifdef CONFIG_RETPOLINE
+ if (exit_reason == EXIT_REASON_MSR_WRITE)
+ return kvm_emulate_wrmsr(vcpu);
+ else if (exit_reason == EXIT_REASON_PREEMPTION_TIMER)
+ return handle_preemption_timer(vcpu);
+ else if (exit_reason == EXIT_REASON_INTERRUPT_WINDOW)
+ return handle_interrupt_window(vcpu);
+ else if (exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT)
+ return handle_external_interrupt(vcpu);
+ else if (exit_reason == EXIT_REASON_HLT)
+ return kvm_emulate_halt(vcpu);
+ else if (exit_reason == EXIT_REASON_EPT_MISCONFIG)
+ return handle_ept_misconfig(vcpu);
+#endif
+
+ exit_reason = array_index_nospec(exit_reason,
+ kvm_vmx_max_exit_handlers);
+ if (!kvm_vmx_exit_handlers[exit_reason])
+ goto unexpected_vmexit;
+
+ return kvm_vmx_exit_handlers[exit_reason](vcpu);
+
+unexpected_vmexit:
+ vcpu_unimpl(vcpu, "vmx: unexpected exit reason 0x%x\n", exit_reason);
+ dump_vmcs();
+ vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+ vcpu->run->internal.suberror =
+ KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON;
+ vcpu->run->internal.ndata = 1;
+ vcpu->run->internal.data[0] = exit_reason;
+ return 0;
}
/*