linux-kernel - [PATCH v2] perf ksymbol: fix memory leak: decrease refcount of map and dso

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Date:   Sat, 12 Jun 2021 19:37:48 +0200
From:   Riccardo Mancini <rickyman7@...il.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Riccardo Mancini <rickyman7@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Tommi Rantala <tommi.t.rantala@...ia.com>,
        Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] perf ksymbol: fix memory leak: decrease refcount of map and dso

ASan reported a memory leak of BPF-related ksymbols
map and dso. The leak is caused by refount never
reaching 0, due to missing __put calls in the function
machine__process_ksymbol_register.
Once the dso is inserted in the map, dso__put should be
called (map__new2 increases the refcount to 2).
The same thing applies for the map when it's inserted
into maps (maps__insert increases the refcount to 2).

$ sudo ./perf record -- sleep 5
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.025 MB perf.data (8 samples) ]

=================================================================
==297735==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 6992 byte(s) in 19 object(s) allocated from:
    #0 0x4f43c7 in calloc (/home/user/linux/tools/perf/perf+0x4f43c7)
    #1 0x8e4e53 in map__new2 /home/user/linux/tools/perf/util/map.c:216:20
    #2 0x8cf68c in machine__process_ksymbol_register /home/user/linux/tools/perf/util/machine.c:778:10
    [...]

Indirect leak of 8702 byte(s) in 19 object(s) allocated from:
    #0 0x4f43c7 in calloc (/home/user/linux/tools/perf/perf+0x4f43c7)
    #1 0x8728d7 in dso__new_id /home/user/linux/tools/perf/util/dso.c:1256:20
    #2 0x872015 in dso__new /home/user/linux/tools/perf/util/dso.c:1295:9
    #3 0x8cf623 in machine__process_ksymbol_register /home/user/linux/tools/perf/util/machine.c:774:21
    [...]

Indirect leak of 1520 byte(s) in 19 object(s) allocated from:
    #0 0x4f43c7 in calloc (/home/user/linux/tools/perf/perf+0x4f43c7)
    #1 0x87b3da in symbol__new /home/user/linux/tools/perf/util/symbol.c:269:23
    #2 0x888954 in map__process_kallsym_symbol /home/user/linux/tools/perf/util/symbol.c:710:8
    [...]

Indirect leak of 1406 byte(s) in 19 object(s) allocated from:
    #0 0x4f43c7 in calloc (/home/user/linux/tools/perf/perf+0x4f43c7)
    #1 0x87b3da in symbol__new /home/user/linux/tools/perf/util/symbol.c:269:23
    #2 0x8cfbd8 in machine__process_ksymbol_register /home/user/linux/tools/perf/util/machine.c:803:8
    [...]

Signed-off-by: Riccardo Mancini <rickyman7@...il.com>
---
 tools/perf/util/machine.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 3ff4936a15a4..da19be7da284 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -776,10 +776,10 @@ static int machine__process_ksymbol_register(struct machine *machine,
 		if (dso) {
 			dso->kernel = DSO_SPACE__KERNEL;
 			map = map__new2(0, dso);
+			dso__put(dso);
 		}
 
 		if (!dso || !map) {
-			dso__put(dso);
 			return -ENOMEM;
 		}
 
@@ -792,6 +792,7 @@ static int machine__process_ksymbol_register(struct machine *machine,
 		map->start = event->ksymbol.addr;
 		map->end = map->start + event->ksymbol.len;
 		maps__insert(&machine->kmaps, map);
+		map__put(map);
 		dso__set_loaded(dso);
 
 		if (is_bpf_image(event->ksymbol.name)) {
-- 
2.23.0