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@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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/events/core.c b/kernel/events/core.c
index bffea4900db1b945d1d76154648dc062a45b17d8..459b94c9472140e1ea2160f070594887d2de60f2 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -190,7 +190,7 @@ 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 f1fa55386100903c0b8902c3ad814dc008753e1b..9469f4c61a30ae67c50a4335a517f4d8074c7015 100644 (file)
--- 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",