[PATCH 3.16 272/366] s390/cpum_sf: ensure sample frequency of perf event attributes is non-zero

Ben Hutchings
2018-10-14T15:25:41Z

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

commit 4bbaf2584b86b0772413edeac22ff448f36351b1 upstream.

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")
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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
arch/s390/kernel/perf_cpum_sf.c | 4 ++++
1 file changed, 4 insertions(+)

--- 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 p
*/
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;