Yeah, but the file system is where I put most of my files. :-)

Between file system, bind/connect, and sending signals, that covers most of it. Probably the biggest remaining risk is any unpatched bugs in the kernel itself.

So one would need to first gain execution in the process, and then elevate that access inside the kernel, in a way that doesn't just grant you root but still Landlocked, and with a much smaller effective syscall attack surface. Like even if there's a kernel bug in ioctl on devs, landlock can turn that off too.