linux-kernel - Re: [PATCH 1/1] perf script: Fix allocation of evsel->priv related to per-event dump files

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Message-ID: <ZIdqvQVkK0vUYw1O@kernel.org>
Date:   Mon, 12 Jun 2023 15:58:05 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Ravi Bangoria <ravi.bangoria@...ux.ibm.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] perf script: Fix allocation of evsel->priv related
 to per-event dump files

Em Tue, Jun 06, 2023 at 04:14:51PM -0700, Ian Rogers escreveu:
> On Tue, Jun 6, 2023 at 12:15 PM Arnaldo Carvalho de Melo
> <acme@...nel.org> wrote:
> >
> > I'm carrying this in my perf-tools-next, please ack :-)
> >
> > - Arnaldo
> >
> > ---
> >
> > When printing output we may want to generate per event files, where the
> > --per-event-dump option should be used, creating perf.data.EVENT.dump
> > files instead of printing to stdout.
> >
> > The callback thar processes event thus expects that evsel->priv->fp
> > should point to either the per-event FILE descriptor or to stdout.
> >
> > The a3af66f51bd0bca7 ("perf script: Fix crash because of missing
> > evsel->priv") changeset fixed a case where evsel->priv wasn't setup,
> > thus set to NULL, causing a segfault when trying to access
> > evsel->priv->fp.
> >
> > But it did it for the non --per-event-dump case by allocating a 'struct
> > perf_evsel_script' just to set its ->fp to stdout.
> >
> > Since evsel->priv is only freed when --per-event-dump is used, we ended
> > up with a memory leek, detected using ASAN.
> 
> nit: s/leek/leak/

Fixed
 
> >
> > Fix it by using the same method as perf_script__setup_per_event_dump(),
> > and reuse that static 'struct perf_evsel_script'.
> >
> > Also check if evsel_script__new() failed.
> >
> > Fixes: a3af66f51bd0bca7 ("perf script: Fix crash because of missing evsel->priv")
> > Reported-by: Ian Rogers <irogers@...gle.com>
> > Cc: Adrian Hunter <adrian.hunter@...el.com>
> > Cc: Jiri Olsa <jolsa@...nel.org>
> > Cc: Namhyung Kim <namhyung@...nel.org>
> > Cc: Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
> > Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> 
> Tested on top of my asan work:
> Tested-by: Ian Rogers <irogers@...gle.com>

Thanks,

- Arnaldo
 
> > ---
> >  tools/perf/builtin-script.c | 16 ++++++++--------
> >  1 file changed, 8 insertions(+), 8 deletions(-)
> >
> > diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
> > index 70549fc93b125394..b02ad386a55baf07 100644
> > --- a/tools/perf/builtin-script.c
> > +++ b/tools/perf/builtin-script.c
> > @@ -2410,6 +2410,9 @@ static int process_sample_event(struct perf_tool *tool,
> >         return ret;
> >  }
> >
> > +// Used when scr->per_event_dump is not set
> > +static struct evsel_script es_stdout;
> > +
> >  static int process_attr(struct perf_tool *tool, union perf_event *event,
> >                         struct evlist **pevlist)
> >  {
> > @@ -2418,7 +2421,6 @@ static int process_attr(struct perf_tool *tool, union perf_event *event,
> >         struct evsel *evsel, *pos;
> >         u64 sample_type;
> >         int err;
> > -       static struct evsel_script *es;
> >
> >         err = perf_event__process_attr(tool, event, pevlist);
> >         if (err)
> > @@ -2428,14 +2430,13 @@ static int process_attr(struct perf_tool *tool, union perf_event *event,
> >         evsel = evlist__last(*pevlist);
> >
> >         if (!evsel->priv) {
> > -               if (scr->per_event_dump) {
> > +               if (scr->per_event_dump) {
> 
> nit: whitespace issue.
> 
> >                         evsel->priv = evsel_script__new(evsel, scr->session->data);
> > -               } else {
> > -                       es = zalloc(sizeof(*es));
> > -                       if (!es)
> > +                       if (!evsel->priv)
> >                                 return -ENOMEM;
> > -                       es->fp = stdout;
> > -                       evsel->priv = es;
> > +               } else { // Replicate what is done in perf_script__setup_per_event_dump()
> > +                       es_stdout.fp = stdout;
> > +                       evsel->priv = &es_stdout;
> >                 }
> >         }
> >
> > @@ -2741,7 +2742,6 @@ static int perf_script__fopen_per_event_dump(struct perf_script *script)
> >  static int perf_script__setup_per_event_dump(struct perf_script *script)
> >  {
> >         struct evsel *evsel;
> > -       static struct evsel_script es_stdout;
> >
> >         if (script->per_event_dump)
> >                 return perf_script__fopen_per_event_dump(script);
> > --
> > 2.37.1
> >

-- 

- Arnaldo