linux-kernel - [PATCH] perf map: Fix refcount errors on Arm with -DREFCNT

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Message-Id: <20230612150424.198914-1-james.clark@arm.com>
Date:   Mon, 12 Jun 2023 16:04:24 +0100
From:   James Clark <james.clark@....com>
To:     linux-perf-users@...r.kernel.org
Cc:     James Clark <james.clark@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] perf map: Fix refcount errors on Arm with -DREFCNT_CHECKING=1

When quitting after running a perf report, the refcount checker finds
some double frees. The issue is that map__put() is called on a function
argument so it removes the refcount wrapper that someone else was using.

Fix it by only calling map__put() on a reference that is owned by this
function.

Signed-off-by: James Clark <james.clark@....com>
---
 tools/perf/util/symbol-elf.c | 9 +++++----
 tools/perf/util/symbol.c     | 9 +++++----
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index 63882a4db5c7..ec0d7810bbb0 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -1365,6 +1365,7 @@ static int dso__process_kernel_symbol(struct dso *dso, struct map *map,
 	struct dso *curr_dso = *curr_dsop;
 	struct map *curr_map;
 	char dso_name[PATH_MAX];
+	struct map *map_ref;
 
 	/* Adjust symbol to map to file offset */
 	if (adjust_kernel_syms)
@@ -1390,10 +1391,10 @@ static int dso__process_kernel_symbol(struct dso *dso, struct map *map,
 			if (kmaps) {
 				int err;
 
-				map__get(map);
-				maps__remove(kmaps, map);
-				err = maps__insert(kmaps, map);
-				map__put(map);
+				map_ref = map__get(map);
+				maps__remove(kmaps, map_ref);
+				err = maps__insert(kmaps, map_ref);
+				map__put(map_ref);
 				if (err)
 					return err;
 			}
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 6b9c55784b56..b3034fd5c0af 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1368,6 +1368,7 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
 	int err, fd;
 	char kcore_filename[PATH_MAX];
 	u64 stext;
+	struct map *map_ref;
 
 	if (!kmaps)
 		return -EINVAL;
@@ -1464,10 +1465,10 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
 			map__set_map_ip(map, map__map_ip_ptr(new_map));
 			map__set_unmap_ip(map, map__unmap_ip_ptr(new_map));
 			/* Ensure maps are correctly ordered */
-			map__get(map);
-			maps__remove(kmaps, map);
-			err = maps__insert(kmaps, map);
-			map__put(map);
+			map_ref = map__get(map);
+			maps__remove(kmaps, map_ref);
+			err = maps__insert(kmaps, map_ref);
+			map__put(map_ref);
 			map__put(new_map);
 			if (err)
 				goto out_err;
-- 
2.34.1