cgroup/cpuset: Fix wrong check in update_parent_subparts_cpumask()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: cgroup/cpuset: Fix wrong check in update_parent_subparts_cpumask() It was found that the check to see if a partition could use up all the cpus from the parent cpuset in update_parent_subparts_cpumask() was incorrect. As a result, it is possible to leave parent with no effective cpu left even if there are tasks in the parent cpuset. This can lead to system panic as reported in [1]. Fix this probem by updating the check to fail the enabling the partition if parent's effective_cpus is a subset of the child's cpus_allowed. Also record the error code when an error happens in update_prstate() and add a test case where parent partition and child have the same cpu list and parent has task. Enabling partition in the child will fail in this case. [1] https://www.spinics.net/lists/cgroups/msg36254.html

References

• https://git.kernel.org/stable/c/a2ab7f2cf5ef8f0c6212a246e681d1fe358cec1f
• https://git.kernel.org/stable/c/e5ae8803847b80fe9d744a3174abe2b7bfed222a