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Chapter 6. Additional security privileges granted for kubevirt-controller and virt-launcher
The kubevirt-controller and virt-launcher pods are granted some SELinux policies and Security Context Constraints privileges that are in addition to typical pod owners. These privileges enable virtual machines to use OpenShift Virtualization features.
6.1. Extended SELinux policies for virt-launcher pods
The container_t SELinux policy for virt-launcher pods is extended to enable essential functions of OpenShift Virtualization.
The following policy is required for network multi-queue, which enables network performance to scale as the number of available vCPUs increases:
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allow process self (tun_socket (relabelfrom relabelto attach_queue))
-
The following policy allows
virt-launcherto read files under the/procdirectory, including/proc/cpuinfoand/proc/uptime:-
allow process proc_type (file (getattr open read))
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The following policy allows
libvirtdto relay network-related debug messages.allow process self (netlink_audit_socket (nlmsg_relay))NoteWithout this policy, any attempt to relay network debug messages is blocked. This might fill the node’s audit logs with SELinux denials.
The following policies allow
libvirtdto accesshugetblfs, which is required to support huge pages:-
allow process hugetlbfs_t (dir (add_name create write remove_name rmdir setattr)) -
allow process hugetlbfs_t (file (create unlink))
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The following policies allow
virtiofsto mount filesystems and access NFS:-
allow process nfs_t (dir (mounton)) -
allow process proc_t (dir (mounton)) -
allow process proc_t (filesystem (mount unmount))
-
6.2. Additional OpenShift Container Platform security context constraints and Linux capabilities for the kubevirt-controller service account
Security context constraints (SCCs) control permissions for pods. These permissions include actions that a pod, a collection of containers, can perform and what resources it can access. You can use SCCs to define a set of conditions that a pod must run with to be accepted into the system.
The kubevirt-controller is a cluster controller that creates the virt-launcher pods for virtual machines in the cluster. These virt-launcher pods are granted permissions by the kubevirt-controller service account.
6.2.1. Additional SCCs granted to the kubevirt-controller service account
The kubevirt-controller service account is granted additional SCCs and Linux capabilities so that it can create virt-launcher pods with the appropriate permissions. These extended permissions allow virtual machines to take advantage of OpenShift Virtualization features that are beyond the scope of typical pods.
The kubevirt-controller service account is granted the following SCCs:
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scc.AllowHostDirVolumePlugin = true
This allows virtual machines to use the hostpath volume plugin. -
scc.AllowPrivilegedContainer = false
This ensures the virt-launcher pod is not run as a privileged container. -
scc.AllowedCapabilities = []corev1.Capability{"NET_ADMIN", "NET_RAW", "SYS_NICE"}
This provides the following additional Linux capabilitiesNET_ADMIN,NET_RAW, andSYS_NICE.
6.2.2. Viewing the SCC and RBAC definitions for the kubevirt-controller
You can view the SecurityContextConstraints definition for the kubevirt-controller by using the oc tool:
$ oc get scc kubevirt-controller -o yaml
You can view the RBAC definition for the kubevirt-controller clusterrole by using the oc tool:
$ oc get clusterrole kubevirt-controller -o yaml
6.3. Additional resources
- Managing security context constraints
- Using RBAC to define and apply permissions
- Optimizing virtual machine network performance in the Red Hat Enterprise Linux (RHEL) documentation
- Using huge pages with virtual machines
- Configuring huge pages in the RHEL documentation
