[PATCH] perf evlist: fix memory corruption for Kernel PMU event

[Barry Song]

Commit 7736627b865d ("perf stat: Use affinity for closing file
descriptors") will use FD(evsel, cpu, thread) to read and write
file descriptors xyarray. For a kernel PMU event, this leads to
serious memory corruption and perf crash.
I have seen evlist->core.cpus->nr is 1 while evsel has cpus->nr
with the total number of CPUs. so xyarray which is allocated by
evlist->core.cpus->nr will get overflow. This leads to various
segmentation faults in perf tool for kernel PMU events, eg:
./perf stat -e bus_cycles  sleep 1
*** Error in `./perf': free(): invalid next size (fast): 0x00000000401e6370 ***
Aborted (core dumped)

Fixes: 7736627b865d ("perf stat: Use affinity for closing file descriptors")
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Alexey Budankov <alexey.budankov@xxxxxxxxxxxxxxx>
Signed-off-by: Barry Song <song.bao.hua@xxxxxxxxxxxxx>
---
 tools/perf/util/evlist.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index c0768c6..3022152 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -1226,10 +1226,14 @@ void evlist__close(struct evlist *evlist)
 	int cpu, i;
 
 	/*
-	 * With perf record core.cpus is usually NULL.
+	 * With perf record core.cpus is usually NULL;
+	 * For Kernel PMU event x, "perf stat -e x" will set evlist->core.cpus->nr to
+	 * 1 while evsel has cpus->nr which contains all CPUs. evsel__cpu_iter_skip()
+	 * will be false, memory corruption will happen if we use affinity to close
+	 * file descriptors;
 	 * Use the old method to handle this for now.
 	 */
-	if (!evlist->core.cpus) {
+	if (!evlist->core.cpus || evlist->core.cpus->nr == 1) {
 		evlist__for_each_entry_reverse(evlist, evsel)
 			evsel__close(evsel);
 		return;
-- 
2.7.4