linux-kernel - Re: [PATCH v1 1/3] perf disasm: Fix capstone memory leak

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Message-ID: <CAP-5=fUCbzz=bLY75DKfdPRNjW91yz6yAzywVe_QWDwK4d7R8g@mail.gmail.com>
Date: Tue, 24 Sep 2024 12:51:20 -0700
From: Ian Rogers <irogers@...gle.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, Kan Liang <kan.liang@...ux.intel.com>, 
	Kajol Jain <kjain@...ux.ibm.com>, Athira Rajeev <atrajeev@...ux.vnet.ibm.com>, 
	"Steinar H. Gunderson" <sesse@...gle.com>, Masami Hiramatsu <mhiramat@...nel.org>, 
	"David S. Miller" <davem@...emloft.net>, Przemek Kitszel <przemyslaw.kitszel@...el.com>, 
	Alexander Lobakin <aleksander.lobakin@...el.com>, Hemant Kumar <hemant@...ux.vnet.ibm.com>, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Yang Jihong <yangjihong@...edance.com>, leo.yan@....com
Subject: Re: [PATCH v1 1/3] perf disasm: Fix capstone memory leak

On Tue, Sep 24, 2024 at 11:38 AM Namhyung Kim <namhyung@...nel.org> wrote:
>
> On Mon, Sep 23, 2024 at 05:37:18PM -0700, Ian Rogers wrote:
> > The insn argument passed to cs_disasm needs freeing. To support
> > accurately having count, add an additional free_count variable.
> >
> > Fixes: c5d60de1813a ("perf annotate: Add support to use libcapstone in powerpc")
> > Signed-off-by: Ian Rogers <irogers@...gle.com>
> > ---
> >  tools/perf/util/disasm.c | 11 +++++++----
> >  1 file changed, 7 insertions(+), 4 deletions(-)
> >
> > diff --git a/tools/perf/util/disasm.c b/tools/perf/util/disasm.c
> > index f05ba7739c1e..2c8063660f2e 100644
> > --- a/tools/perf/util/disasm.c
> > +++ b/tools/perf/util/disasm.c
> > @@ -1627,12 +1627,12 @@ static int symbol__disassemble_capstone(char *filename, struct symbol *sym,
> >       u64 start = map__rip_2objdump(map, sym->start);
> >       u64 len;
> >       u64 offset;
> > -     int i, count;
> > +     int i, count, free_count;
> >       bool is_64bit = false;
> >       bool needs_cs_close = false;
> >       u8 *buf = NULL;
> >       csh handle;
> > -     cs_insn *insn;
> > +     cs_insn *insn = NULL;
> >       char disasm_buf[512];
> >       struct disasm_line *dl;
> >
> > @@ -1664,7 +1664,7 @@ static int symbol__disassemble_capstone(char *filename, struct symbol *sym,
> >
> >       needs_cs_close = true;
> >
> > -     count = cs_disasm(handle, buf, len, start, len, &insn);
> > +     free_count = count = cs_disasm(handle, buf, len, start, len, &insn);
> >       for (i = 0, offset = 0; i < count; i++) {
> >               int printed;
> >
> > @@ -1702,8 +1702,11 @@ static int symbol__disassemble_capstone(char *filename, struct symbol *sym,
> >       }
> >
> >  out:
> > -     if (needs_cs_close)
> > +     if (needs_cs_close) {
> >               cs_close(&handle);
> > +             if (free_count > 0)
> > +                     cs_free(insn, free_count);
>
> It seems cs_free() can handle NULL insn and 0 free_count (like regular free)
> so we can call it unconditionally.

No, on error from cs_disasm free_count gets assigned -1 and my
experience was things crashing.

Thanks,
Ian

>
> > +     }
> >       free(buf);
> >       return count < 0 ? count : 0;
> >
> > --
> > 2.46.0.792.g87dc391469-goog
> >