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linux/kernel
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Ethan Zhao 21a24b5db1 sched/sysctl: Check user input value of sysctl_sched_time_avg 
commit 5ccba44ba1 upstream.

System will hang if user set sysctl_sched_time_avg to 0:

  [root@XXX ~]# sysctl kernel.sched_time_avg_ms=0

  Stack traceback for pid 0
  0xffff883f6406c600 0 0 1 3 R 0xffff883f6406cf50 *swapper/3
  ffff883f7ccc3ae8 0000000000000018 ffffffff810c4dd0 0000000000000000
  0000000000017800 ffff883f7ccc3d78 0000000000000003 ffff883f7ccc3bf8
  ffffffff810c4fc9 ffff883f7ccc3c08 00000000810c5043 ffff883f7ccc3c08
  Call Trace:
  <IRQ> [<ffffffff810c4dd0>] ? update_group_capacity+0x110/0x200
  [<ffffffff810c4fc9>] ? update_sd_lb_stats+0x109/0x600
  [<ffffffff810c5507>] ? find_busiest_group+0x47/0x530
  [<ffffffff810c5b84>] ? load_balance+0x194/0x900
  [<ffffffff810ad5ca>] ? update_rq_clock.part.83+0x1a/0xe0
  [<ffffffff810c6d42>] ? rebalance_domains+0x152/0x290
  [<ffffffff810c6f5c>] ? run_rebalance_domains+0xdc/0x1d0
  [<ffffffff8108a75b>] ? __do_softirq+0xfb/0x320
  [<ffffffff8108ac85>] ? irq_exit+0x125/0x130
  [<ffffffff810b3a17>] ? scheduler_ipi+0x97/0x160
  [<ffffffff81052709>] ? smp_reschedule_interrupt+0x29/0x30
  [<ffffffff8173a1be>] ? reschedule_interrupt+0x6e/0x80
   <EOI> [<ffffffff815bc83c>] ? cpuidle_enter_state+0xcc/0x230
  [<ffffffff815bc80c>] ? cpuidle_enter_state+0x9c/0x230
  [<ffffffff815bc9d7>] ? cpuidle_enter+0x17/0x20
  [<ffffffff810cd6dc>] ? cpu_startup_entry+0x38c/0x420
  [<ffffffff81053373>] ? start_secondary+0x173/0x1e0

Because divide-by-zero error happens in function:

update_group_capacity()
  update_cpu_capacity()
    scale_rt_capacity()
     {
          ...
          total = sched_avg_period() + delta;
          used = div_u64(avg, total);
          ...
     }

To fix this issue, check user input value of sysctl_sched_time_avg, keep
it unchanged when hitting invalid input, and set the minimum limit of
sysctl_sched_time_avg to 1 ms.

Reported-by: James Puthukattukaran <james.puthukattukaran@oracle.com>
Signed-off-by: Ethan Zhao <ethan.zhao@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: efault@gmx.de
Cc: ethan.kernel@gmail.com
Cc: keescook@chromium.org
Cc: mcgrof@kernel.org
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/1504504774-18253-1-git-send-email-ethan.zhao@oracle.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Steve Muckle <smuckle@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2018-09-05 09:18:33 +02:00
..
bpf
bpf: fix references to free_bpf_prog_info() in comments
2018-08-06 16:24:37 +02:00
configs
kconfig: tinyconfig: provide whole choice blocks to avoid warnings
2016-09-24 10:07:42 +02:00
debug
kdb: make "mdr" command repeat
2018-05-30 07:49:17 +02:00
events
perf/core: Fix perf_output_read_group()
2018-05-30 07:49:12 +02:00
gcov
gcov: disable for COMPILE_TEST
2018-01-23 19:50:10 +01:00
irq
genirq: Make force irq threading setup more robust
2018-08-09 12:19:27 +02:00
livepatch
livepatch: x86: fix relocation computation with kASLR
2015-11-11 17:36:04 +01:00
locking
locking/lockdep: Do not record IRQ state within lockdep code
2018-08-24 13:26:55 +02:00
power
PM / hibernate: Fix oops at snapshot_write()
2018-07-17 11:31:46 +02:00
printk
braille-console: Fix value returned by _braille_console_setup
2018-03-22 09:23:23 +01:00
rcu
rcu: Allow for page faults in NMI handlers
2017-10-18 09:20:41 +02:00
sched
sched/rt: Fix rq->clock_update_flags < RQCF_ACT_SKIP warning
2018-05-30 07:49:08 +02:00
time
nohz: Fix local_timer_softirq_pending()
2018-08-09 12:19:27 +02:00
trace
tracing: Use __printf markup to silence compiler
2018-08-24 13:26:58 +02:00
.gitignore
certs: add .gitignore to stop git nagging about x509_certificate_list
2015-10-21 15:18:35 +01:00
acct.c
kernel/acct.c: fix the acct->needcheck check in check_free_space()
2018-01-10 09:27:08 +01:00
async.c
kernel/async.c: revert "async: simplify lowest_in_progress()"
2018-02-16 20:09:45 +01:00
audit_fsnotify.c
audit: clean simple fsnotify implementation
2015-08-06 16:14:53 -04:00
audit_tree.c
audit: audit_tree_match can be boolean
2015-11-04 08:23:51 -05:00
audit_watch.c
audit: Fix use after free in audit_remove_watch_rule()
2017-08-24 17:02:35 -07:00
audit.c
audit: return on memory error to avoid null pointer dereference
2018-05-30 07:49:16 +02:00
audit.h
audit: audit_tree_match can be boolean
2015-11-04 08:23:51 -05:00
auditfilter.c
audit: allow not equal op for audit by executable
2018-08-06 16:24:38 +02:00
auditsc.c
audit: allow not equal op for audit by executable
2018-08-06 16:24:38 +02:00
backtracetest.c
…
bounds.c
…
capability.c
exec: Ensure mm->user_ns contains the execed files
2017-01-06 11:16:14 +01:00
cgroup_freezer.c
cgroup: fix handling of multi-destination migration from subtree_control enabling
2015-12-03 10:18:21 -05:00
cgroup_pids.c
cgroup_pids: don't account for the root cgroup
2015-12-03 10:18:21 -05:00
cgroup.c
cgroup, kthread: close race window where new kthreads can be migrated to non-root cgroups
2017-04-21 09:30:04 +02:00
compat.c
compat: cleanup coding in compat_get_bitmap() and compat_put_bitmap()
2015-06-04 23:57:18 +02:00
configs.c
…
context_tracking.c
context_tracking: avoid irq_save/irq_restore on guest entry and exit
2015-11-10 12:06:23 +01:00
cpu_pm.c
kernel/cpu_pm: fix cpu_cluster_pm_exit comment
2015-09-03 02:42:20 +02:00
cpu.c
stable-fixup: hotplug: fix unused function warning
2017-01-12 11:22:48 +01:00
cpuset.c
sched/cpuset/pm: Fix cpuset vs. suspend-resume bugs
2017-10-12 11:27:35 +02:00
crash_dump.c
…
cred.c
cred: Reject inodes with invalid ids in set_create_file_as()
2016-09-15 08:27:49 +02:00
delayacct.c
…
dma.c
…
elfcore.c
…
exec_domain.c
…
exit.c
kernel/exit.c: avoid undefined behaviour when calling wait4()
2018-05-26 08:48:51 +02:00
extable.c
kernel/extable.c: mark core_kernel_text notrace
2017-07-21 07:44:56 +02:00
fork.c
kaiser: stack map PAGE_SIZE at THREAD_SIZE-PAGE_SIZE
2018-01-05 15:44:23 +01:00
freezer.c
…
futex_compat.c
ptrace: use fsuid, fsgid, effective creds for fs access checks
2016-02-25 12:01:16 -08:00
futex.c
futex: futex_wake_op, fix sign_extend32 sign bits
2018-05-26 08:48:51 +02:00
groups.c
kernel: make groups_sort calling a responsibility group_info allocators
2018-01-10 09:27:10 +01:00
hung_task.c
…
irq_work.c
treewide: Remove old email address
2015-11-23 09:44:58 +01:00
jump_label.c
jump_label: Invoke jump_label_test() via early_initcall()
2017-12-16 10:33:55 +01:00
kallsyms.c
…
kcmp.c
ptrace: use fsuid, fsgid, effective creds for fs access checks
2016-02-25 12:01:16 -08:00
Kconfig.freezer
…
Kconfig.hz
…
Kconfig.locks
…
Kconfig.preempt
…
kexec_core.c
kexec: use file name as the output message prefix
2015-11-06 17:50:42 -08:00
kexec_file.c
kexec: fix double-free when failing to relocate the purgatory
2016-09-24 10:07:36 +02:00
kexec_internal.h
kexec: split kexec_file syscall code to kexec_file.c
2015-09-10 13:29:01 -07:00
kexec.c
kexec: use file name as the output message prefix
2015-11-06 17:50:42 -08:00
kmod.c
kmod: don't run async usermode helper as a child of kworker thread
2015-10-23 17:55:10 +09:00
kprobes.c
kprobes/x86: Fix to set RWX bits correctly before releasing trampoline
2018-04-08 11:51:56 +02:00
ksysfs.c
kexec: split kexec_load syscall from kexec core code
2015-09-10 13:29:01 -07:00
kthread.c
cgroup, kthread: close race window where new kthreads can be migrated to non-root cgroups
2017-04-21 09:30:04 +02:00
latencytop.c
…
Makefile
sys_membarrier(): system-wide memory barrier (generic, x86)
2015-09-11 15:21:34 -07:00
membarrier.c
Fix: Disable sys_membarrier when nohz_full is enabled
2017-03-12 06:37:26 +01:00
memremap.c
mm: fix devm_memremap_pages crash, use mem_hotplug_{begin, done}
2017-01-19 20:17:18 +01:00
module_signing.c
KEYS: Merge the type-specific data with the payload data
2015-10-21 15:18:36 +01:00
module-internal.h
…
module.c
module/retpoline: Warn about missing retpoline in module
2018-02-25 11:03:52 +01:00
notifier.c
Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
2015-09-01 08:40:25 -07:00
nsproxy.c
…
padata.c
padata: free correct variable
2017-05-20 14:27:02 +02:00
panic.c
kernel/panic.c: add missing \n
2017-07-05 14:37:19 +02:00
params.c
Merge tag 'modules-next-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux
2015-11-09 15:53:39 -08:00
pid_namespace.c
pid_ns: Sleep in TASK_INTERRUPTIBLE in zap_pid_ns_processes
2017-05-25 14:30:11 +02:00
pid.c
pidns: disable pid allocation if pid_ns_prepare_proc() is failed in alloc_pid()
2018-04-13 19:50:03 +02:00
profile.c
profile: hide unused functions when !CONFIG_PROC_FS
2018-02-25 11:03:44 +01:00
ptrace.c
ptrace: Properly initialize ptracer_cred on fork
2017-06-14 13:16:20 +02:00
range.c
…
reboot.c
kexec: split kexec_load syscall from kexec core code
2015-09-10 13:29:01 -07:00
relay.c
kernel/relay.c: limit kmalloc size to KMALLOC_MAX_SIZE
2018-05-30 07:49:00 +02:00
resource.c
resource: fix integer overflow at reallocation
2018-04-24 09:32:05 +02:00
seccomp.c
seccomp: Move speculation migitation control to arch code
2018-07-25 10:18:27 +02:00
signal.c
kernel/signal.c: avoid undefined behaviour in kill_something_info
2018-05-30 07:48:52 +02:00
smp.c
mm, page_alloc: distinguish between being unable to sleep, unwilling to sleep and avoiding waking kswapd
2015-11-06 17:50:42 -08:00
smpboot.c
stop_machine: Kill smp_hotplug_thread->pre_unpark, introduce stop_machine_unpark()
2015-10-20 10:23:55 +02:00
smpboot.h
…
softirq.c
…
stacktrace.c
…
stop_machine.c
kernel: remove stop_machine() Kconfig dependency
2015-12-12 10:15:34 -08:00
sys_ni.c
mm: mlock: add new mlock system call
2015-11-05 19:34:48 -08:00
sys.c
nospec: Allow getting/setting on non-current task
2018-07-25 10:18:26 +02:00
sysctl_binary.c
fs/coredump: prevent fsuid=0 dumps into user-controlled directories
2016-04-12 09:08:58 -07:00
sysctl.c
sched/sysctl: Check user input value of sysctl_sched_time_avg
2018-09-05 09:18:33 +02:00
task_work.c
task_work: remove fifo ordering guarantee
2015-09-05 13:46:58 -07:00
taskstats.c
…
test_kprobes.c
…
torture.c
torture: Consolidate cond_resched_rcu_qs() into stutter_wait()
2015-10-06 11:25:01 -07:00
tracepoint.c
tracepoint: Do not warn on ENOMEM
2018-05-16 10:06:47 +02:00
tsacct.c
…
uid16.c
kernel: make groups_sort calling a responsibility group_info allocators
2018-01-10 09:27:10 +01:00
up.c
…
user_namespace.c
capabilities: ambient capabilities
2015-09-04 16:54:41 -07:00
user-return-notifier.c
…
user.c
…
utsname_sysctl.c
…
utsname.c
…
watchdog.c
kernel/watchdog: use nmi registers snapshot in hardlockup handler
2017-01-06 11:16:16 +01:00
workqueue_internal.h
workqueue: Fix NULL pointer dereference
2017-11-15 17:13:11 +01:00
workqueue.c
workqueue: use put_device() instead of kfree()
2018-05-30 07:49:04 +02:00