From: Hendrik Brueckner <brueckner@linux.ibm.com>
Date: Thu, 3 May 2018 15:56:15 +0200
Subject: s390/cpum_sf: ensure sample frequency of perf event attributes is
 non-zero
Git-commit: 4bbaf2584b86b0772413edeac22ff448f36351b1
Patch-mainline: v4.17-rc6
References: bnc#1096753, LTC#168037

Correct a trinity finding for the perf_event_open() system call with
a perf event attribute structure that uses a frequency but has the
sampling frequency set to zero.  This causes a FP divide exception during
the sample rate initialization for the hardware sampling facility.

Fixes: 8c069ff4bd606 ("s390/perf: add support for the CPU-Measurement Sampling Facility")
Cc: stable@vger.kernel.org # 3.14+
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Hendrik Brueckner <brueckner@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Acked-by: Johannes Thumshirn <jthumshirn@suse.de>
---
 arch/s390/kernel/perf_cpum_sf.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/s390/kernel/perf_cpum_sf.c b/arch/s390/kernel/perf_cpum_sf.c
index 1c9ddd7aa5ec..0292d68e7dde 100644
--- a/arch/s390/kernel/perf_cpum_sf.c
+++ b/arch/s390/kernel/perf_cpum_sf.c
@@ -753,6 +753,10 @@ static int __hw_perf_event_init(struct perf_event *event)
 	 */
 	rate = 0;
 	if (attr->freq) {
+		if (!attr->sample_freq) {
+			err = -EINVAL;
+			goto out;
+		}
 		rate = freq_to_sample_rate(&si, attr->sample_freq);
 		rate = hw_limit_rate(&si, rate);
 		attr->freq = 0;