Re: [PATCH v1] perf symbol: Avoid use after free

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Tue, Mar 28, 2023 at 10:35:07PM -0700, Ian Rogers escreveu:
> On Tue, Mar 28, 2023 at 9:52 PM Adrian Hunter <adrian.hunter@intel.com> wrote:
> >
> > On 29/03/23 02:44, Ian Rogers wrote:
> > > If demangling succeeds then sym_name is set to the demangled string
> > > that is freed. Rather than test if sym_name is empty and possibly
> > > use-after-free on the return path, expand out the alternatives.
> >
> > Looks the same as:
> >
> > https://lore.kernel.org/linux-perf-users/20230316194156.8320-2-adrian.hunter@intel.com/
> 
> Sorry for missing that. In the case it returns false, this avoids an
> unnecessary snprintf.

I applied Adrian's fixes,

- Arnaldo
 
> Thanks,
> Ian
> 
> > >
> > > Signed-off-by: Ian Rogers <irogers@google.com>
> > > ---
> > >  tools/perf/util/symbol-elf.c | 18 ++++++++++--------
> > >  1 file changed, 10 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
> > > index c0a2de42c51b..b7e3e492bff3 100644
> > > --- a/tools/perf/util/symbol-elf.c
> > > +++ b/tools/perf/util/symbol-elf.c
> > > @@ -577,15 +577,17 @@ static bool get_plt_got_name(GElf_Shdr *shdr, size_t i,
> > >       /* Get the associated symbol */
> > >       gelf_getsym(di->dynsym_data, vr->sym_idx, &sym);
> > >       sym_name = elf_sym__name(&sym, di->dynstr_data);
> > > -     demangled = demangle_sym(di->dso, 0, sym_name);
> > > -     if (demangled != NULL)
> > > -             sym_name = demangled;
> > > -
> > > -     snprintf(buf, buf_sz, "%s@plt", sym_name);
> > > -
> > > -     free(demangled);
> > > +     if (*sym_name == '\0')
> > > +             return false;
> > >
> > > -     return *sym_name;
> > > +     demangled = demangle_sym(di->dso, 0, sym_name);
> > > +     if (demangled != NULL) {
> > > +             snprintf(buf, buf_sz, "%s@plt", demangled);
> > > +             free(demangled);
> > > +     } else {
> > > +             snprintf(buf, buf_sz, "%s@plt", sym_name);
> > > +     }
> > > +     return true;
> > >  }
> > >
> > >  static int dso__synthesize_plt_got_symbols(struct dso *dso, Elf *elf,
> >

-- 

- Arnaldo