On 1/17/19 11:15 AM, Tejun Heo wrote:
Hello,
On Thu, Jan 17, 2019 at 10:01:23AM -0500, Daniel Walsh wrote:
The above comment is correct. We want to be able to run a container
where we hand it control over a limited subdir of the cgroups hierachy.
We can currently do this and label the content correctly, but when
subdirs of the directory get created by processes inside the container
they do not get the correct label. For example we add a label like
system_u:object_r:container_file_t:s0 to a directory but when the
process inside of the container creates a fd within this directory the
kernel says the label is the default label for cgroups
system_u:object_r:cgroup_t:s0. This forces us to write looser policy
that from an SELinux point of view allows a process within the container
to write anywhere on the cgroup file system, rather then just the
designated directories.
Can you please go into a bit more details on why the existing
cgroup delegation model isn't enough?
I would hazard a guess that it is because the existing cgroup delegation
model is based on user IDs and discretionary access control (DAC),
whereas they are using per-container SELinux security contexts and
mandatory access control (MAC) to enforce the separation of containers
irrespective of UID and DAC. Optimally both would be supported by
cgroup, as DAC and MAC have different properties and use cases.
