[tip:sched/core] sched/sysctl: Check user input value of sysctl_sched_time_avg

Path	csiph.com!aioe.org!bofh.it!news.nic.it!robomod
From	tip-bot for Ethan Zhao <tipbot@zytor.com>
Newsgroups	linux.kernel
Subject	[tip:sched/core] sched/sysctl: Check user input value of sysctl_sched_time_avg
Date	Fri, 29 Sep 2017 22:20:02 +0200
Message-ID	<uv9Vo-2wp-7@gated-at.bofh.it> (permalink)
References	<ulSK6-1QU-9@gated-at.bofh.it>
X-Original-To	linux-tip-commits@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
Git-Commit-ID	5ccba44ba118a5000cccc50076b0344632459779
X-Mailer	tip-git-log-daemon
Robot-ID	<tip-bot.git.kernel.org>
Robot-Unsubscribe	Contact <mailto:hpa@kernel.org> 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	robomod@news.nic.it
List-ID	<linux-kernel.vger.kernel.org>
X-Mailing-List	linux-kernel@vger.kernel.org
Approved	robomod@news.nic.it
Lines	84
Organization	linux.* mail to news gateway
X-Original-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
X-Original-Date	Fri, 29 Sep 2017 13:06:42 -0700
X-Original-Message-ID	<tip-5ccba44ba118a5000cccc50076b0344632459779@git.kernel.org>
X-Original-References	<1504504774-18253-1-git-send-email-ethan.zhao@oracle.com>
X-Original-Sender	linux-kernel-owner@vger.kernel.org
Xref	csiph.com linux.kernel:1742319

Show key headers only | View raw

Commit-ID:  5ccba44ba118a5000cccc50076b0344632459779
Gitweb:     https://git.kernel.org/tip/5ccba44ba118a5000cccc50076b0344632459779
Author:     Ethan Zhao <ethan.zhao@oracle.com>
AuthorDate: Mon, 4 Sep 2017 13:59:34 +0800
Committer:  Ingo Molnar <mingo@kernel.org>
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:
  <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>
---
 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
 	{

Back to linux.kernel | Previous | Next | Find similar | Unroll thread

Thread

[tip:sched/core] sched/sysctl: Check user input value of  sysctl_sched_time_avg tip-bot for Ethan Zhao <tipbot@zytor.com> - 2017-09-29 22:20 +0200

csiph-web