lkml.org 
[lkml]   [2013]   [Sep]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH] perf: Prevent divide by zero exception in kernel/events/core.c
Any value written to /proc/sys/kernel/perf_event_max_sample_rate
is accepted and used as a divisor in perf_proc_update_handler().

Obviously that is wrong. 0 will cause a divide by 0 exception,
and negative values are unreasonable.

The attached patch enforces a lower limit of 1.

cu,
Knut
From 7f468bd7bad2f2fec2e93c89a48008d1cba99001 Mon Sep 17 00:00:00 2001
From: Knut Petersen <Knut_Petersen@t-online.de>
Date: Wed, 25 Sep 2013 13:34:57 +0200
Subject: [PATCH] Enforce 1 as lower limit for perf_event_max_sample_rate

/proc/sys/kernel/perf_event_max_sample_rate will accept
negative values as well as 0.

Negative values are unreasonable, and 0 causes a
divide by zero exception in perf_proc_update_handler.

This patch enforces a lower limit of 1.

Signed-off-by: Knut Petersen <Knut_Petersen@t-online.de>
---
kernel/events/core.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index dd236b6..350bb53 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -198,6 +198,9 @@ int perf_proc_update_handler(struct ctl_table *table, int write,
if (ret || !write)
return ret;

+ if (sysctl_perf_event_sample_rate <= 0)
+ sysctl_perf_event_sample_rate = 1;
+
max_samples_per_tick = DIV_ROUND_UP(sysctl_perf_event_sample_rate, HZ);
perf_sample_period_ns = NSEC_PER_SEC / sysctl_perf_event_sample_rate;
update_perf_cpu_limits();
--
1.8.1.4
\
 
 \ /
  Last update: 2013-09-25 14:41    [W:0.038 / U:1.008 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site