s390/cpum_sf: ensure sample frequency of perf event attributes is non-zero

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>

diff --git a/arch/s390/kernel/perf_cpum_sf.c b/arch/s390/kernel/perf_cpum_sf.c
index 1c9ddd7..0292d68 100644 (file)
--- 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;