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Subject[PATCH 3.11 066/131] perf: Enforce 1 as lower limit for perf_event_max_sample_rate
Date
3.11.10.6 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Knut Petersen <Knut_Petersen@t-online.de>

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@t-online.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/5242DB0C.4070005@t-online.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Weng Meiling <wengmeiling.weng@huawei.com>
Signed-off-by: Luis Henriques <luis.henriques@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


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