Re: [PATCH] perf map: Fix namespace memory leak

[Arnaldo Carvalho de Melo]

Em Sun, Nov 28, 2021 at 04:40:26PM +0100, Jiri Olsa escreveu:
> On Thu, Nov 18, 2021 at 11:37:14AM -0800, Ian Rogers wrote:
> > This leak was happening reliably with test "Lookup mmap thread" with
> > stack traces like:
> > 
> > Direct leak of 5504 byte(s) in 172 object(s) allocated from:
> >     #0 0x7f4685e47987 in __interceptor_calloc
> >     #1 0x56063b974c2a in nsinfo__new util/namespaces.c:142
> >     #2 0x56063b9781ff in thread__new util/thread.c:70
> >     #3 0x56063b944953 in ____machine__findnew_thread util/machine.c:543
> >     #4 0x56063b944ac6 in __machine__findnew_thread util/machine.c:574
> >     #5 0x56063b944b36 in machine__findnew_thread util/machine.c:584
> >     #6 0x56063b94c892 in machine__process_fork_event util/machine.c:1954
> >     #7 0x56063b94cc1f in machine__process_event util/machine.c:2019
> >     #8 0x56063b894f18 in perf_event__process util/event.c:567
> >     #9 0x56063ba17951 in perf_tool__process_synth_event util/synthetic-events.c:65
> >     #10 0x56063ba19086 in perf_event__synthesize_fork util/synthetic-events.c:287
> >     #11 0x56063ba1c39d in __event__synthesize_thread util/synthetic-events.c:775
> >     #12 0x56063ba1cf6f in __perf_event__synthesize_threads util/synthetic-events.c:929
> >     #13 0x56063ba1d4ab in perf_event__synthesize_threads util/synthetic-events.c:1000
> >     #14 0x56063b821a3d in synth_all tests/mmap-thread-lookup.c:136
> >     #15 0x56063b821c86 in mmap_events tests/mmap-thread-lookup.c:174
> >     #16 0x56063b8221b7 in test__mmap_thread_lookup tests/mmap-thread-lookup.c:230
> > 
> > The dso->nsinfo is overwritten, but without a nsinfo__put this can leak
> > the overwritten nsinfo.
> > 
> > Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
> 
> nice catch!
> 
> Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>

This one is tricky, I have to retrieve the details from last time this
surfaced, but try:

# perf top -F 10000

leave it for a while and press 'q':

perf: /home/acme/git/perf/tools/include/linux/refcount.h:131: refcount_sub_and_test: Assertion `!(new > val)' failed.
                                                                                                                     Aborted (core dumped)

I reproduced the above assertion a few times, now I'm not being able,
probably some namespace related activity took place when it hit.

- Arnaldo
 
> thanks,
> jirka
> 
> > ---
> >  tools/perf/util/map.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
> > index 8af693d9678c..ceed8f407bc0 100644
> > --- a/tools/perf/util/map.c
> > +++ b/tools/perf/util/map.c
> > @@ -192,6 +192,7 @@ struct map *map__new(struct machine *machine, u64 start, u64 len,
> >  			if (!(prot & PROT_EXEC))
> >  				dso__set_loaded(dso);
> >  		}
> > +		nsinfo__put(dso->nsinfo);
> >  		dso->nsinfo = nsi;
> >  
> >  		if (build_id__is_defined(bid))
> > -- 
> > 2.34.0.rc2.393.gf8c9666880-goog
> > 

-- 

- Arnaldo