linux-kernel - [PATCH v1] perf test cpumap: Avoid use-after-free following merge

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Message-Id: <20250108051511.1720369-1-irogers@google.com>
Date: Tue,  7 Jan 2025 21:15:11 -0800
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Kan Liang <kan.liang@...ux.intel.com>, Leo Yan <leo.yan@....com>, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1] 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: a9d2217556f7 ("libperf cpumap: Refactor perf_cpu_map__merge()")
Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/tests/cpumap.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tools/perf/tests/cpumap.c b/tools/perf/tests/cpumap.c
index 5ed7ff072ea3..2354246afc5a 100644
--- a/tools/perf/tests/cpumap.c
+++ b/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;
 }
-- 
2.47.1.613.gc27f4b7a9f-goog