CVE-2023-52831

In the Linux kernel, the following vulnerability has been resolved:
cpu/hotplug: Don’t offline the last non-isolated CPU If a system has
isolated CPUs via the “isolcpus=” command line parameter, then an attempt
to offline the last housekeeping CPU will result in a WARN_ON() when
rebuilding the scheduler domains and a subsequent panic due to and
unhandled empty CPU mas in partition_sched_domains_locked().
cpuset_hotplug_workfn() rebuild_sched_domains_locked() ndoms =
generate_sched_domains(&doms, &attr); cpumask_and(doms[0],
top_cpuset.effective_cpus, housekeeping_cpumask(HK_FLAG_DOMAIN)); Thus
results in an empty CPU mask which triggers the warning and then the
subsequent crash: WARNING: CPU: 4 PID: 80 at kernel/sched/topology.c:2366
build_sched_domains+0x120c/0x1408 Call trace:
build_sched_domains+0x120c/0x1408
partition_sched_domains_locked+0x234/0x880
rebuild_sched_domains_locked+0x37c/0x798 rebuild_sched_domains+0x30/0x58
cpuset_hotplug_workfn+0x2a8/0x930 Unable to handle kernel paging request at
virtual address fffe80027ab37080 partition_sched_domains_locked+0x318/0x880
rebuild_sched_domains_locked+0x37c/0x798 Aside of the resulting crash, it
does not make any sense to offline the last last housekeeping CPU. Prevent
this by masking out the non-housekeeping CPUs when selecting a target CPU
for initiating the CPU unplug operation via the work queue.