From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Ian Rogers <irogers@google.com>
Cc: Riccardo Mancini <rickyman7@gmail.com>,
Namhyung Kim <namhyung@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@redhat.com>,
Adrian Hunter <adrian.hunter@intel.com>,
Andi Kleen <ak@linux.intel.com>,
Tommi Rantala <tommi.t.rantala@nokia.com>,
linux-perf-users <linux-perf-users@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] perf ksymbol: fix memory leak: decrease refcount of map and dso
Date: Fri, 4 Jun 2021 10:22:56 -0300 [thread overview]
Message-ID: <YLopMBgLWysdJbkm@kernel.org> (raw)
In-Reply-To: <CAP-5=fVxHUnwGoRypMjCsPSh_yo5PB8Hzbkx5ArA5b0=7S-67g@mail.gmail.com>
Em Thu, Jun 03, 2021 at 09:26:40PM -0700, Ian Rogers escreveu:
> On Wed, Jun 2, 2021 at 4:15 PM Riccardo Mancini <rickyman7@gmail.com> wrote:
> > +++ b/tools/perf/util/machine.c
> > @@ -776,6 +776,7 @@ static int machine__process_ksymbol_register(struct machine *machine,
> > if (dso) {
> > dso->kernel = DSO_SPACE__KERNEL;
> > map = map__new2(0, dso);
> > + dso__put(dso);
> Will this cause 2 puts if the map allocation fails? Perhaps this
> should be "if (map) dso__put(dso);".
I think its just a matter of removing the put in the error path, i.e.
the patch becomes what is at the end of this message.
I.e. if map__new2() fails, we want to drop the dso reference, and if it
works, we already have a reference to it, obtained in map__new2().
But looking at this code now I realize that maps__find() should grab a
refcount for the map it returns, because in this
machine__process_ksymbol_register() function we use reference that 'map'
after the if block, i.e. we use it if it came from maps__find() or if we
created it machine__process_ksymbol_register, so there is a possible
race where other thread removes it from the list and map__put()s it
ending up in map__delete() while we still use it in
machine__process_ksymbol_register(), right?
- Arnaldo
> > }
> > if (!dso || !map) {
> > @@ -792,6 +793,7 @@ 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)) {
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 3ff4936a15a42f74..da19be7da284c250 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)) {
next prev parent reply other threads:[~2021-06-04 13:23 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-02 23:10 [PATCH] perf ksymbol: fix memory leak: decrease refcount of map and dso Riccardo Mancini
2021-06-04 4:26 ` Ian Rogers
2021-06-04 13:22 ` Arnaldo Carvalho de Melo [this message]
2021-06-04 15:16 ` Riccardo Mancini
2021-06-04 18:29 ` Arnaldo Carvalho de Melo
2021-06-12 17:37 ` [PATCH v2] " Riccardo Mancini
2021-06-16 18:12 ` Arnaldo Carvalho de Melo
2021-06-18 10:01 ` [PATCH] " Riccardo Mancini
2021-06-18 13:25 ` Arnaldo Carvalho de Melo
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