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

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Date:   Wed, 16 Jun 2021 15:12:42 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Riccardo Mancini <rickyman7@...il.com>
Cc:     Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.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: Re: [PATCH v2] perf ksymbol: fix memory leak: decrease refcount of
 map and dso

Em Sat, Jun 12, 2021 at 07:37:48PM +0200, Riccardo Mancini escreveu:
> 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).

Thanks, applied.

- Arnaldo

 
> $ 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
> 

-- 

- Arnaldo