linux-kernel - Re: [PATCH 01/20] perf nsinfo: fix refcounting

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Message-ID: <YPCQDK7dQhLNAWGT@kernel.org>
Date:   Thu, 15 Jul 2021 16:44:12 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Riccardo Mancini <rickyman7@...il.com>
Cc:     Krister Johansen <kjlx@...pleofstupid.com>,
        Ian Rogers <irogers@...gle.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Jiri Olsa <jolsa@...hat.com>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH 01/20] perf nsinfo: fix refcounting

Em Thu, Jul 15, 2021 at 04:02:16PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Thu, Jul 15, 2021 at 06:07:06PM +0200, Riccardo Mancini escreveu:
> > ASan reports a memory leak of nsinfo during the execution of the perf
> > test "31: Lookup mmap thread".
> > The leak is caused by a refcounted variable being replaced without
> > dropping the refcount.
> > 
> > This patch makes sure that the refcnt of nsinfo is decreased whenever
> > a refcounted variable is replaced with a new value.
> 
> So, there are multiple fixes in just one patch, I'll split it into
> three, no need to resend.
> 
> I'll try and check if finding Fixes: for the three is easy, that way
> stable@...r.kernel.org will figure out which of the supported releases
> need each of them.

3rd:

commit 7416120498f83963f4c5662847a1a0556e771b89
Author: Riccardo Mancini <rickyman7@...il.com>
Date:   Thu Jul 15 18:07:06 2021 +0200

    perf probe: Fix dso->nsinfo refcounting
    
    ASan reports a memory leak of nsinfo during the execution of:
    
     # perf test "31: Lookup mmap thread".
    
    The leak is caused by a refcounted variable being replaced without
    dropping the refcount.
    
    This patch makes sure that the refcnt of nsinfo is decreased whenever
    a refcounted variable is replaced with a new value.
    
    Signed-off-by: Riccardo Mancini <rickyman7@...il.com>
    Fixes: 544abd44c7064c8a ("perf probe: Allow placing uprobes in alternate namespaces.")
    Cc: Ian Rogers <irogers@...gle.com>
    Cc: Jiri Olsa <jolsa@...hat.com>
    Cc: Krister Johansen <kjlx@...pleofstupid.com>
    Cc: Mark Rutland <mark.rutland@....com>
    Cc: Namhyung Kim <namhyung@...nel.org>
    Cc: Peter Zijlstra <peterz@...radead.org>
    Link: http://lore.kernel.org/lkml/55223bc8821b34ccb01f92ef1401c02b6a32e61f.1626343282.git.rickyman7@gmail.com
    [ Split from a larger patch ]
    Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index c14e1d228e56b1c6..e05750cea34c3a95 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -179,8 +179,10 @@ struct map *get_target_map(const char *target, struct nsinfo *nsi, bool user)
 		struct map *map;
 
 		map = dso__new_map(target);
-		if (map && map->dso)
+		if (map && map->dso) {
+			nsinfo__put(map->dso->nsinfo);
 			map->dso->nsinfo = nsinfo__get(nsi);
+		}
 		return map;
 	} else {
 		return kernel_get_module_map(target);