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Daniel Jordan 6eab3f646b cpuset: fix race between hotplug work and later CPU offline 
commit 406100f3da upstream.

One of our machines keeled over trying to rebuild the scheduler domains.
Mainline produces the same splat:

  BUG: unable to handle page fault for address: 0000607f820054db
  CPU: 2 PID: 149 Comm: kworker/1:1 Not tainted 5.10.0-rc1-master+ #6
  Workqueue: events cpuset_hotplug_workfn
  RIP: build_sched_domains
  Call Trace:
   partition_sched_domains_locked
   rebuild_sched_domains_locked
   cpuset_hotplug_workfn

It happens with cgroup2 and exclusive cpusets only.  This reproducer
triggers it on an 8-cpu vm and works most effectively with no
preexisting child cgroups:

  cd $UNIFIED_ROOT
  mkdir cg1
  echo 4-7 > cg1/cpuset.cpus
  echo root > cg1/cpuset.cpus.partition

  # with smt/control reading 'on',
  echo off > /sys/devices/system/cpu/smt/control

RIP maps to

  sd->shared = *per_cpu_ptr(sdd->sds, sd_id);

from sd_init().  sd_id is calculated earlier in the same function:

  cpumask_and(sched_domain_span(sd), cpu_map, tl->mask(cpu));
  sd_id = cpumask_first(sched_domain_span(sd));

tl->mask(cpu), which reads cpu_sibling_map on x86, returns an empty mask
and so cpumask_first() returns >= nr_cpu_ids, which leads to the bogus
value from per_cpu_ptr() above.

The problem is a race between cpuset_hotplug_workfn() and a later
offline of CPU N.  cpuset_hotplug_workfn() updates the effective masks
when N is still online, the offline clears N from cpu_sibling_map, and
then the worker uses the stale effective masks that still have N to
generate the scheduling domains, leading the worker to read
N's empty cpu_sibling_map in sd_init().

rebuild_sched_domains_locked() prevented the race during the cgroup2
cpuset series up until the Fixes commit changed its check.  Make the
check more robust so that it can detect an offline CPU in any exclusive
cpuset's effective mask, not just the top one.

Fixes: 0ccea8feb9 ("cpuset: Make generate_sched_domains() work with partition")
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20201112171711.639541-1-daniel.m.jordan@oracle.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2020-12-30 11:51:36 +01:00
..
bpf bpf: Zero-fill re-used per-cpu map element 2020-11-18 19:20:26 +01:00
cgroup cpuset: fix race between hotplug work and later CPU offline 2020-12-30 11:51:36 +01:00
configs
…
debug kgdb: Make "kgdbcon" work properly with "kgdb_earlycon" 2020-11-05 11:43:16 +01:00
dma swiotlb: fix "x86: Don't panic if can not alloc buffer for swiotlb" 2020-11-18 19:20:32 +01:00
events perf/core: Fix race in the perf_mmap_close() function 2020-11-18 19:20:33 +01:00
gcov gcov: add support for GCC 10.1 2020-09-17 13:47:56 +02:00
irq genirq/irqdomain: Don't try to free an interrupt that has no mapping 2020-12-30 11:51:14 +01:00
livepatch livepatch: Nullify obj->mod in klp_module_coming()'s error path 2019-08-19 13:03:37 +02:00
locking locking/lockdep: Decrement IRQ context counters when removing lock chain 2020-10-01 13:17:33 +02:00
power PM: hibernate: remove the bogus call to get_gendisk() in software_resume() 2020-10-29 09:58:04 +01:00
printk printk: handle blank console arguments passed in. 2020-10-01 13:18:04 +02:00
rcu arm64: smp: Tell RCU about CPUs that fail to come online 2020-11-24 13:29:01 +01:00
sched sched: Reenable interrupts in do_sched_yield() 2020-12-30 11:51:03 +01:00
time tick/common: Touch watchdog in tick_unfreeze() on all CPUs 2020-11-18 19:20:26 +01:00
trace bpf: Fix bpf_put_raw_tracepoint()'s use of __module_address() 2020-12-30 11:51:18 +01:00
.gitignore Provide in-kernel headers to make extending kernel easier 2019-04-29 16:48:03 +02:00
Kconfig.freezer treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
Kconfig.hz treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
Kconfig.locks treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
Kconfig.preempt sched/rt, Kconfig: Unbreak def/oldconfig with CONFIG_PREEMPT=y 2019-07-22 18:05:11 +02:00
Makefile kernel/sysctl-test: Add null pointer test for sysctl.c:proc_dointvec() 2020-10-01 13:17:10 +02:00
acct.c
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async.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441 2019-06-05 17:37:17 +02:00
audit.c audit: fix a net reference leak in audit_list_rules_send() 2020-06-22 09:30:59 +02:00
audit.h audit: fix a net reference leak in audit_list_rules_send() 2020-06-22 09:30:59 +02:00
audit_fsnotify.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 157 2019-05-30 11:26:37 -07:00
audit_tree.c fsnotify: switch send_to_group() and ->handle_event to const struct qstr * 2019-04-26 13:51:03 -04:00
audit_watch.c audit: CONFIG_CHANGE don't log internal bookkeeping as an event 2020-10-01 13:17:32 +02:00
auditfilter.c audit: fix a net reference leak in audit_list_rules_send() 2020-06-22 09:30:59 +02:00
auditsc.c audit: enforce op for string fields 2019-05-28 17:46:43 -04:00
backtracetest.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441 2019-06-05 17:37:17 +02:00
bounds.c
…
capability.c
…
compat.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
configs.c kernel/configs: Replace GPL boilerplate code with SPDX identifier 2019-07-30 18:34:15 +02:00
context_tracking.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
cpu.c kernel/cpu: add arch override for clear_tasks_mm_cpumask() mm handling 2020-12-30 11:50:56 +01:00
cpu_pm.c kernel/cpu_pm: Fix uninitted local in cpu_pm 2020-06-22 09:31:22 +02:00
crash_core.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 230 2019-06-19 17:09:06 +02:00
crash_dump.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
cred.c keys: Fix request_key() cache 2020-01-17 19:48:42 +01:00
delayacct.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 25 2019-05-21 11:52:39 +02:00
dma.c
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elfcore.c kernel/elfcore.c: include proper prototypes 2019-09-25 17:51:39 -07:00
exec_domain.c
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exit.c don't dump the threads that had been already exiting when zapped. 2020-11-18 19:20:31 +01:00
extable.c extable: Add function to search only kernel exception table 2019-08-21 22:23:48 +10:00
fail_function.c fail_function: Remove a redundant mutex unlock 2020-11-24 13:29:18 +01:00
fork.c fork: fix copy_process(CLONE_PARENT) race with the exiting ->real_parent 2020-11-10 12:37:32 +01:00
freezer.c Revert "libata, freezer: avoid block device removal while system is frozen" 2019-10-06 09:11:37 -06:00
futex.c futex: Don't enable IRQs unconditionally in put_pi_state() 2020-11-18 19:20:30 +01:00
gen_kheaders.sh kbuild: add variables for compression tools 2020-09-03 11:27:10 +02:00
groups.c
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hung_task.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
iomem.c mm/nvdimm: add is_ioremap_addr and use that to check ioremap address 2019-07-12 11:05:40 -07:00
irq_work.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
jump_label.c jump_label: Don't warn on __exit jump entries 2019-08-29 15:10:10 +01:00
kallsyms.c kallsyms: Refactor kallsyms_show_value() to take cred 2020-07-16 08:16:44 +02:00
kcmp.c kernel/kcmp.c: Use new infrastructure to fix deadlocks in execve 2020-10-01 13:17:48 +02:00
kcov.c
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kexec.c kexec_load: Disable at runtime if the kernel is locked down 2019-08-19 21:54:15 -07:00
kexec_core.c kexec: bail out upon SIGKILL when allocating memory. 2019-09-25 17:51:40 -07:00
kexec_elf.c kexec_elf: support 32 bit ELF files 2019-09-06 23:58:44 +02:00
kexec_file.c Merge branch 'next-lockdown' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2019-09-28 08:14:15 -07:00
kexec_internal.h
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kheaders.c kheaders: Move from proc to sysfs 2019-05-24 20:16:01 +02:00
kmod.c kmod: make request_module() return an error when autoloading is disabled 2020-04-17 10:50:22 +02:00
kprobes.c kprobes: Fix compiler warning for !CONFIG_KPROBES_ON_FTRACE 2020-10-01 13:18:25 +02:00
ksysfs.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 170 2019-05-30 11:26:39 -07:00
kthread.c kthread_worker: prevent queuing delayed work from timer_fn when it is being canceled 2020-11-10 12:37:27 +01:00
latencytop.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441 2019-06-05 17:37:17 +02:00
module-internal.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36 2019-05-24 17:27:11 +02:00
module.c module: statically initialize init section freeing data 2020-10-29 09:57:55 +01:00
module_signature.c MODSIGN: Export module signature definitions 2019-08-05 18:39:56 -04:00
module_signing.c MODSIGN: Export module signature definitions 2019-08-05 18:39:56 -04:00
notifier.c kernel/notifier.c: intercept duplicate registrations to avoid infinite loops 2020-10-01 13:17:23 +02:00
nsproxy.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441 2019-06-05 17:37:17 +02:00
padata.c padata: add separate cpuhp node for CPUHP_PADATA_DEAD 2020-06-17 16:40:22 +02:00
panic.c panic: ensure preemption is disabled during panic() 2019-10-07 15:47:19 -07:00
params.c lockdown: Lock down module params that specify hardware parameters (eg. ioport) 2019-08-19 21:54:16 -07:00
pid.c kernel/pid.c: convert struct pid count to refcount_t 2019-07-16 19:23:24 -07:00
pid_namespace.c proc/sysctl: add shared variables for range check 2019-07-18 17:08:07 -07:00
profile.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
ptrace.c ptrace: Set PF_SUPERPRIV when checking capability 2020-11-24 13:29:24 +01:00
range.c
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reboot.c reboot: fix overflow parsing reboot cpu number 2020-11-18 19:20:30 +01:00
relay.c kernel/relay.c: fix memleak on destroy relay channel 2020-08-26 10:40:51 +02:00
resource.c /dev/mem: Revoke mappings when a driver claims the region 2020-06-24 17:50:35 +02:00
rseq.c signal: Remove task parameter from force_sig 2019-05-27 09:36:28 -05:00
seccomp.c seccomp: Set PF_SUPERPRIV when checking capability 2020-11-24 13:29:24 +01:00
signal.c ptrace: fix task_join_group_stop() for the case when current is traced 2020-11-10 12:37:24 +01:00
smp.c smp: Warn on function calls from softirq context 2019-07-20 11:27:16 +02:00
smpboot.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
smpboot.h
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softirq.c Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-07-08 11:01:13 -07:00
stackleak.c
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stacktrace.c stacktrace: Don't skip first entry on noncurrent tasks 2019-11-04 21:19:25 +01:00
stop_machine.c stop_machine: Avoid potential race behaviour 2019-10-17 12:47:12 +02:00
sys.c kernel/sys.c: avoid copying possible padding bytes in copy_to_user 2020-10-01 13:17:23 +02:00
sys_ni.c arch: handle arches who do not yet define clone3 2019-06-21 01:54:53 +02:00
sysctl-test.c kernel/sysctl-test: Add null pointer test for sysctl.c:proc_dointvec() 2020-10-01 13:17:10 +02:00
sysctl.c kernel: sysctl: make drop_caches write-only 2020-01-04 19:18:32 +01:00
sysctl_binary.c
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task_work.c
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taskstats.c taskstats: fix data-race 2020-01-09 10:19:54 +01:00
test_kprobes.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 25 2019-05-21 11:52:39 +02:00
torture.c torture: Remove exporting of internal functions 2019-08-01 14:30:22 -07:00
tracepoint.c The main changes in this release include: 2019-07-18 11:51:00 -07:00
tsacct.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 157 2019-05-30 11:26:37 -07:00
ucount.c proc/sysctl: add shared variables for range check 2019-07-18 17:08:07 -07:00
uid16.c
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uid16.h
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umh.c usermodehelper: reset umask to default before executing user process 2020-10-14 10:32:58 +02:00
up.c smp: Remove smp_call_function() and on_each_cpu() return values 2019-06-23 14:26:26 +02:00
user-return-notifier.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
user.c Keyrings namespacing 2019-07-08 19:36:47 -07:00
user_namespace.c Keyrings namespacing 2019-07-08 19:36:47 -07:00
utsname.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441 2019-06-05 17:37:17 +02:00
utsname_sysctl.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441 2019-06-05 17:37:17 +02:00
watchdog.c watchdog/softlockup: Enforce that timestamp is valid on boot 2020-02-24 08:36:52 +01:00
watchdog_hld.c kernel/watchdog_hld.c: hard lockup message should end with a newline 2019-04-19 09:46:05 -07:00
workqueue.c workqueue: Remove the warning in wq_worker_sleeping() 2020-10-01 13:17:54 +02:00
workqueue_internal.h sched/core, workqueues: Distangle worker accounting from rq lock 2019-04-16 16:55:15 +02:00