perf test cpumap: Avoid use-after-free following merge

Previously cpu maps in the test weren't modified by calls to the cpu map
API, however, perf_cpu_map__merge was modified so the left hand argument
was updated.

In the test this meant the maps copy of the "two" map was put/deleted in
the merge meaning when accessed via maps, the pointer was stale and to
the put/deleted memory.

To fix this add an extra layer of indirection to the maps array, so the
updated value of two is accessed.

Fixes: a9d2217 ("libperf cpumap: Refactor perf_cpu_map__merge()")
Reviewed-by: James Clark <[email protected]>
Signed-off-by: Ian Rogers <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: Leo Yan <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Author: captain5050

tools/perf/tests/cpumap.c

@@ -252,16 +252,16 @@ static int test__cpu_map_equal(struct test_suite *test __maybe_unused, int subte
 	struct perf_cpu_map *empty = perf_cpu_map__intersect(one, two);
 	struct perf_cpu_map *pair = perf_cpu_map__new("1-2");
 	struct perf_cpu_map *tmp;
-	struct perf_cpu_map *maps[] = {empty, any, one, two, pair};
+	struct perf_cpu_map **maps[] = {&empty, &any, &one, &two, &pair};
 
 	for (size_t i = 0; i < ARRAY_SIZE(maps); i++) {
 		/* Maps equal themself. */
-		TEST_ASSERT_VAL("equal", perf_cpu_map__equal(maps[i], maps[i]));
+		TEST_ASSERT_VAL("equal", perf_cpu_map__equal(*maps[i], *maps[i]));
 		for (size_t j = 0; j < ARRAY_SIZE(maps); j++) {
 			/* Maps dont't equal each other. */
 			if (i == j)
 				continue;
-			TEST_ASSERT_VAL("not equal", !perf_cpu_map__equal(maps[i], maps[j]));
+			TEST_ASSERT_VAL("not equal", !perf_cpu_map__equal(*maps[i], *maps[j]));
 		}
 	}
 
@@ -274,7 +274,7 @@ static int test__cpu_map_equal(struct test_suite *test __maybe_unused, int subte
 	perf_cpu_map__put(tmp);
 
 	for (size_t i = 0; i < ARRAY_SIZE(maps); i++)
-		perf_cpu_map__put(maps[i]);
+		perf_cpu_map__put(*maps[i]);
 
 	return TEST_OK;
 }