That's right. Docker still runs without user namespaces by default, which means that root is the same user inside and outside of the container. This does open up attack surface and configuration footguns.
replyConfinement still leverages dropping some root caps, seccomp, various other namespaces, etc.
I don't think this is true, otherwise you could just load a kernel module into the host kernel from a container.
replyRoot is not just one thing on modern Linux, almost all in-kernel privilege checks are now gated via (slightly) more fine-grained capabilities and the default capability set for Docker containers disallows module loading (CAP_SYS_MODULE) and the relevant syscalls (namely (f)init_module) are also blocked with seccomp.
replyPeople still should use user namespaces (and tools like Podman and Incus do by default) but basic stuff like that is not the reason.
There are a million ways to load a kernel module from inside of a container into the host kernel (ie: to trigger a load), but seccomp/ linux caps will block the direct ways (as another commenter notes).
replyIt is very possible to load a kernel module into the host from a container.
replyhttps://stackoverflow.com/questions/33013539/docker-loading-...
Presumably Docker's seccomp profile [1] blocks the init_module system call which is used by insmod [2]. Although, looking at the default profile, it seems to explicitly allow it - but maybe only if you have CAP_SYS_MODULE, which I think means running Docker with "--cap-add=SYS_MODULE".
replyAt least podman does if running rootless, I assume docker supports rootless operation as well.
replyNot sure about running rootful though. I don't really use rootful containers personally.