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Yes, we have proven that shared-kernel multitenant is unsafe. The best example (though there are many) is the `waitid` LPE; nobody's container lockdown configuration was blocking `waitid`, which is what you'd have had to do to prevent container code from compromising the kernel. The list of Linux LPEs is long, and syzkaller crashes longer stil.

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https://news.ycombinator.com/item?id=40591147

So the PaaS providers mentioned in that comment should be assumed to be compromised?

If they are using multitenant Docker / containerd containers with no additional sandboxing, then yes, then it's only a matter of time and attacker interest before a cross-tenant compromise occurs.

There isn't realistic sandboxing you can do with shared-kernel multitenant general-workload runtimes. You can do shared-kernel with a language runtime, like V8 isolates. You can do it with WASM. But you can't do native binary Unix execution and count on sandboxing to fix the security issues, because there's a track record of local LPEs in benign system calls.

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