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

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Message-ID: <lsq.1539530741.882871538@decadent.org.uk>
Date:   Sun, 14 Oct 2018 16:25:41 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Hendrik Brueckner" <brueckner@...ux.ibm.com>,
        "Martin Schwidefsky" <schwidefsky@...ibm.com>,
        "Heiko Carstens" <heiko.carstens@...ibm.com>
Subject: [PATCH 3.16 272/366] s390/cpum_sf: ensure sample frequency of
 perf event attributes is non-zero

3.16.60-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Hendrik Brueckner <brueckner@...ux.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@...ibm.com>
Signed-off-by: Hendrik Brueckner <brueckner@...ux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
Signed-off-by: Ben Hutchings <ben@...adent.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;