k8s: root cannot chown in emptyDir volume mount

Maybe this is expected, but I'm facing workloads that are failing under sysbox because root can't change the owner of files and directories in a shared volume mount.

Create my pod:

apiVersion: v1
kind: Pod
metadata:
  name: sysbox-test
  namespace: default
  annotations:
    io.kubernetes.cri-o.userns-mode: "auto:size=65536"
spec:
  runtimeClassName: sysbox-runc
  containers:
    - name: ubu-bio-systemd-docker
      image: registry.nestybox.com/nestybox/ubuntu-bionic-systemd-docker
      command: ["/sbin/init"]
      volumeMounts:
        - mountPath: /tmp/share
          name: share
    - name: foo
      image: ubuntu
      command: ["/bin/sleep", "180"]
      securityContext:
        runAsUser: 999
        runAsGroup: 999
      volumeMounts:
        - mountPath: /tmp/share
          name: share
  securityContext:
    fsGroup: 999

  restartPolicy: Always
  volumes:
    - name: share
      emptyDir:
        medium: Memory

Then from the shell on the system container:

kubectl exec -it sysbox-test -- /bin/bash

root@sysbox-test:/# mkdir /tmp/share/foo
root@sysbox-test:/# ls -lhd /tmp/share/foo/
drwxr-sr-x 2 root nogroup 40 May 25 18:20 /tmp/share/foo/
root@sysbox-test:/# chown 999:999 /tmp/share/foo/
chown: changing ownership of '/tmp/share/foo/': Operation not permitted

I can workaround, but this works without sysbox.

Start with the provided Kubernetes pod manifest and reproduce the failure using the kubectl exec commands. Trace how sysbox handles emptyDir shared-volume ownership changes and compare the behavior with and without sysbox. Done means root can chown files and directories in the shared emptyDir mount without the reported Operation not permitted error.