[SRU][Xenial][Artful][Bionic][PATCH 1/1] s390/cpum_sf: ensure sample frequency of perf event attributes is non-zero

[Joseph Salisbury]

From: Hendrik Brueckner <brueckner at linux.ibm.com>

BugLink: http://bugs.launchpad.net/bugs/1772593

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 at vger.kernel.org # 3.14+
Reviewed-by: Heiko Carstens <heiko.carstens at de.ibm.com>
Signed-off-by: Hendrik Brueckner <brueckner at linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky at de.ibm.com>
(cherry picked from commit 4bbaf2584b86b0772413edeac22ff448f36351b1)
Signed-off-by: Joseph Salisbury <joseph.salisbury at canonical.com>
---
 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 3d8da1e..b79d514 100644
--- a/arch/s390/kernel/perf_cpum_sf.c
+++ b/arch/s390/kernel/perf_cpum_sf.c
@@ -744,6 +744,10 @@ 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;
-- 
2.7.4