From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752534AbdI2UKW (ORCPT ); Fri, 29 Sep 2017 16:10:22 -0400 Received: from terminus.zytor.com ([65.50.211.136]:58493 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752113AbdI2UKU (ORCPT ); Fri, 29 Sep 2017 16:10:20 -0400 Date: Fri, 29 Sep 2017 13:06:42 -0700 From: tip-bot for Ethan Zhao Message-ID: Cc: torvalds@linux-foundation.org, james.puthukattukaran@oracle.com, ethan.zhao@oracle.com, stable@vger.kernel.org, peterz@infradead.org, mingo@kernel.org, hpa@zytor.com, tglx@linutronix.de, linux-kernel@vger.kernel.org Reply-To: james.puthukattukaran@oracle.com, torvalds@linux-foundation.org, peterz@infradead.org, mingo@kernel.org, stable@vger.kernel.org, ethan.zhao@oracle.com, linux-kernel@vger.kernel.org, hpa@zytor.com, tglx@linutronix.de In-Reply-To: <1504504774-18253-1-git-send-email-ethan.zhao@oracle.com> References: <1504504774-18253-1-git-send-email-ethan.zhao@oracle.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched/sysctl: Check user input value of sysctl_sched_time_avg Git-Commit-ID: 5ccba44ba118a5000cccc50076b0344632459779 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 5ccba44ba118a5000cccc50076b0344632459779 Gitweb: https://git.kernel.org/tip/5ccba44ba118a5000cccc50076b0344632459779 Author: Ethan Zhao AuthorDate: Mon, 4 Sep 2017 13:59:34 +0800 Committer: Ingo Molnar CommitDate: Fri, 29 Sep 2017 13:20:13 +0200 sched/sysctl: Check user input value of sysctl_sched_time_avg 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: [] ? update_group_capacity+0x110/0x200 [] ? update_sd_lb_stats+0x109/0x600 [] ? find_busiest_group+0x47/0x530 [] ? load_balance+0x194/0x900 [] ? update_rq_clock.part.83+0x1a/0xe0 [] ? rebalance_domains+0x152/0x290 [] ? run_rebalance_domains+0xdc/0x1d0 [] ? __do_softirq+0xfb/0x320 [] ? irq_exit+0x125/0x130 [] ? scheduler_ipi+0x97/0x160 [] ? smp_reschedule_interrupt+0x29/0x30 [] ? reschedule_interrupt+0x6e/0x80 [] ? cpuidle_enter_state+0xcc/0x230 [] ? cpuidle_enter_state+0x9c/0x230 [] ? cpuidle_enter+0x17/0x20 [] ? cpu_startup_entry+0x38c/0x420 [] ? 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 Signed-off-by: Ethan Zhao Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: efault@gmx.de Cc: ethan.kernel@gmail.com Cc: keescook@chromium.org Cc: mcgrof@kernel.org Cc: Link: http://lkml.kernel.org/r/1504504774-18253-1-git-send-email-ethan.zhao@oracle.com Signed-off-by: Ingo Molnar --- kernel/sysctl.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 6648fbb..423554a 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 {