linux-kernel - [PATCH v2 4/6] perf maps: Get map before returning in maps__find_next

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Date: Wed,  7 Feb 2024 14:36:37 -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>, Song Liu <song@...nel.org>, 
	Miguel Ojeda <ojeda@...nel.org>, Liam Howlett <liam.howlett@...cle.com>, 
	Colin Ian King <colin.i.king@...il.com>, K Prateek Nayak <kprateek.nayak@....com>, 
	Artem Savkov <asavkov@...hat.com>, Changbin Du <changbin.du@...wei.com>, 
	Masami Hiramatsu <mhiramat@...nel.org>, Athira Rajeev <atrajeev@...ux.vnet.ibm.com>, 
	Yang Jihong <yangjihong1@...wei.com>, Tiezhu Yang <yangtiezhu@...ngson.cn>, 
	James Clark <james.clark@....com>, Leo Yan <leo.yan@...aro.org>, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
	bpf@...r.kernel.org
Subject: [PATCH v2 4/6] perf maps: Get map before returning in maps__find_next_entry

Finding a map is done under a lock, returning the map without a
reference count means it can be removed without notice and causing
uses after free. Grab a reference count to the map within the lock
region and return this. Fix up locations that need a map__put
following this.

Signed-off-by: Ian Rogers <irogers@...gle.com>
Acked-by: Namhyung Kim <namhyung@...nel.org>
---
 tools/perf/util/machine.c | 4 +++-
 tools/perf/util/maps.c    | 2 +-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 7031f6fddcae..4911734411b5 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1761,8 +1761,10 @@ int machine__create_kernel_maps(struct machine *machine)
 		struct map *next = maps__find_next_entry(machine__kernel_maps(machine),
 							 machine__kernel_map(machine));
 
-		if (next)
+		if (next) {
 			machine__set_kernel_mmap(machine, start, map__start(next));
+			map__put(next);
+		}
 	}
 
 out_put:
diff --git a/tools/perf/util/maps.c b/tools/perf/util/maps.c
index f4855e2bfd6e..e577909456be 100644
--- a/tools/perf/util/maps.c
+++ b/tools/perf/util/maps.c
@@ -956,7 +956,7 @@ struct map *maps__find_next_entry(struct maps *maps, struct map *map)
 	down_read(maps__lock(maps));
 	i = maps__by_address_index(maps, map);
 	if (i < maps__nr_maps(maps))
-		result = maps__maps_by_address(maps)[i]; // TODO: map__get
+		result = map__get(maps__maps_by_address(maps)[i]);
 
 	up_read(maps__lock(maps));
 	return result;
-- 
2.43.0.594.gd9cf4e227d-goog