linux-kernel - [PATCH v3 41/50] perf maps: Get map before returning in maps__find_next

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Message-Id: <20231024222353.3024098-42-irogers@google.com>
Date:   Tue, 24 Oct 2023 15:23:44 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     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>,
        Nick Terrell <terrelln@...com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>, Leo Yan <leo.yan@...aro.org>,
        Song Liu <song@...nel.org>,
        Sandipan Das <sandipan.das@....com>,
        James Clark <james.clark@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Miguel Ojeda <ojeda@...nel.org>,
        Liam Howlett <liam.howlett@...cle.com>,
        Yang Jihong <yangjihong1@...wei.com>,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
        Kajol Jain <kjain@...ux.ibm.com>,
        K Prateek Nayak <kprateek.nayak@....com>,
        Sean Christopherson <seanjc@...gle.com>,
        Yanteng Si <siyanteng@...ngson.cn>,
        Ravi Bangoria <ravi.bangoria@....com>,
        German Gomez <german.gomez@....com>,
        Changbin Du <changbin.du@...wei.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        liuwenyu <liuwenyu7@...wei.com>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org
Subject: [PATCH v3 41/50] 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>
---
 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 d6b3f84cb935..42d73f00f9c1 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1758,8 +1758,10 @@ 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 8a8c1f216b86..b3937e734cbf 100644
--- a/tools/perf/util/maps.c
+++ b/tools/perf/util/maps.c
@@ -942,7 +942,7 @@ 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;
-- 
2.42.0.758.gaed0368e0e-goog