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authorEthan Zhao <ethan.zhao@oracle.com>2017-09-04 13:59:34 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-10-05 09:47:33 +0200
commitde8c137cb712c65f59f4e97e5a3b90d75b7edf59 (patch)
tree680f0a289524397dfb9d281e18aef4efe471840c
parentc8b679ba7c65457e45af7c086c5df0748522aa2f (diff)
sched/sysctl: Check user input value of sysctl_sched_time_avg
commit 5ccba44ba118a5000cccc50076b0344632459779 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 Link: http://lkml.kernel.org/r/1504504774-18253-1-git-send-email-ethan.zhao@oracle.com Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--kernel/sysctl.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 6648fbbb8157..423554ad3610 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -367,7 +367,8 @@ static struct ctl_table kern_table[] = {
.data = &sysctl_sched_time_avg,
.maxlen = sizeof(unsigned int),
.mode = 0644,
- .proc_handler = proc_dointvec,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &one,
},
#ifdef CONFIG_SCHEDSTATS
{