They currently go out of their way to remove microarchitectural side channels. Yes, there's almost certainly others, but it's pretty clear that the end goal is to allow non root creation of bpf programs.
Is it really possible to remove the side channels? Even if you formally prove that it does not access memory outside of authorized regions, that doesn't prevent it from speculatively accessing unauthorized memory.
We've seen Spectre exploits through sandboxed Javascript. Unless you separated the eBPF VM address space from the kernel address space, I suspect you would have the exact same problems that browsers have had. But if you did put them in separate address spaces, then why bother with eBPF? You could run a normal userspace program.
eBPF right now issues fence instructions before computed address loads, in order to manually shutdown speculative instructions. They also do a cute trick to compute the address with a mask so that if a speculative access does happen, the speculatively computed offset is still in the valid range.
