CVE-2023-52831 Information

Description

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.

Reference

https://git.kernel.org/stable/c/3410b702354702b500bde10e3cc1f9db8731d908 https://git.kernel.org/stable/c/335a47ed71e332c82339d1aec0c7f6caccfcda13 https://git.kernel.org/stable/c/3073f6df783d9d75f7f69f73e16c7ef85d6cfb63 https://git.kernel.org/stable/c/38685e2a0476127db766f81b1c06019ddc4c9ffa