> Until we fix this RCE vulnerability, the attacker will 
    > still be able to execute code on our host [...]

With Docker, it seems to me like we're moving closer and closer to the server being an executable of its own, but with the necessary Linux kernel bits compiled in such that it can execute on (virtualized) hardware.

I'm wondering how far we can take this. The ability to execute code on the host is there because that's what Linux does, but what if we removed this interface, and replaced it with an interface that just accepts one or more ELF binaries at compile-time? Then these would become the only Linux executables that this kernel can execute.

As far as I can see, we could do the same to system calls: if an executable can enumerate all the system calls it needs, we can compile a kernel that will accept only these system calls, which should be a small subset of all available Linux syscalls.