[3.11.y.z extended stable] Patch "perf: Enforce 1 as lower limit for perf_event_max_sample_rate" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    perf: Enforce 1 as lower limit for perf_event_max_sample_rate

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 31b9cfd89e50f24fae58082e7dd35fb946b4861e Mon Sep 17 00:00:00 2001
From: Knut Petersen <Knut_Petersen at t-online.de>
Date: Wed, 25 Sep 2013 14:29:37 +0200
Subject: perf: Enforce 1 as lower limit for perf_event_max_sample_rate

commit 723478c8a471403c53cf144999701f6e0c4bbd11 upstream.

/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 at t-online.de>
Signed-off-by: Peter Zijlstra <peterz at infradead.org>
Link: http://lkml.kernel.org/r/5242DB0C.4070005@t-online.de
Signed-off-by: Ingo Molnar <mingo at kernel.org>
Cc: Weng Meiling <wengmeiling.weng at huawei.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 kernel/events/core.c | 2 +-
 kernel/sysctl.c      | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index f86599e..fc645f1 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -192,7 +192,7 @@ int perf_proc_update_handler(struct ctl_table *table, int write,
 		void __user *buffer, size_t *lenp,
 		loff_t *ppos)
 {
-	int ret = proc_dointvec(table, write, buffer, lenp, ppos);
+	int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);

 	if (ret || !write)
 		return ret;
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 07f6fc4..f252045 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1049,6 +1049,7 @@ static struct ctl_table kern_table[] = {
 		.maxlen		= sizeof(sysctl_perf_event_sample_rate),
 		.mode		= 0644,
 		.proc_handler	= perf_proc_update_handler,
+		.extra1		= &one,
 	},
 	{
 		.procname	= "perf_cpu_time_max_percent",
--
1.9.0