I guess thats overly dramatic. The big touchscreen (and I guess the only thing that actually runs a Linux) is called an infotainment system for a reason - it's absolutely non-critical to the operation of the vehicle. In fact, theres a hotkey on the steering wheel controls to reboot it :)

All the critical systems are controlled by embedded systems running either no operating system at all or realtime operating systems that have been formally verified to some degree.