From: Ran Xiaokai ran.xiaokai@zte.com.cn

mainline inclusion from mainline-v6.7-rc1 commit 38685e2a0476127db766f81b1c06019ddc4c9ffa category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9RFL2 CVE: CVE-2023-52831

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...

--------------------------------

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.

Suggested-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Ran Xiaokai ran.xiaokai@zte.com.cn Signed-off-by: Thomas Gleixner tglx@linutronix.de Link: https://lore.kernel.org/r/202310171709530660462@zte.com.cn Conflicts: kernel/cpu.c [commit 04d4e665a60902cf36e7ad39af1179cb5df542ad ("sched/isolation: Use single feature type while referring to housekeeping cpumask") was nos merged] Signed-off-by: liwei liwei728@huawei.com --- kernel/cpu.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/kernel/cpu.c b/kernel/cpu.c index fdd911b306e0..870ac4283f86 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -1142,11 +1142,14 @@ static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target) /* * Ensure that the control task does not run on the to be offlined * CPU to prevent a deadlock against cfs_b->period_timer. + * Also keep at least one housekeeping cpu onlined to avoid generating + * an empty sched_domain span. */ - cpu = cpumask_any_but(cpu_online_mask, cpu); - if (cpu >= nr_cpu_ids) - return -EBUSY; - return work_on_cpu(cpu, __cpu_down_maps_locked, &work); + for_each_cpu_and(cpu, cpu_online_mask, housekeeping_cpumask(HK_FLAG_DOMAIN)) { + if (cpu != work.cpu) + return work_on_cpu(cpu, __cpu_down_maps_locked, &work); + } + return -EBUSY; }

static int cpu_down(unsigned int cpu, enum cpuhp_state target)