I work on multi-tenant k8s clusters at CDNs and used to work at Rancher and have seen just about every multi-tenant / federated deployment there is, nasa, meta, etc. Stuff where even the hardware vfio paths mounting the nic or gpu channels keep users apart from one another, and the entire path out of the cluster are completely apart from k8s and any userspace and would be something like multus as a shim- what exactly are you referring to that can cgroup hop via a shell that we're not currently mitigating? It's the hardware being infected by something we worry about at this level.

A lot of the CDNs even use tools like kubevirt where the segmentation is even further. And then we have gvisor, firecracker, etc.

I admittedly haven't touched k8s code since 1.18 but I can't think of anything like you're referring to and I definitely would like to know about it.

Thanks.