Re: [PATCH v2] perf trace: Fix possible insufficient allocation of argument formats

[Howard Chu]

Hello Namhyung,

On Thu, Mar 27, 2025 at 12:16 AM Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
>
> Hello,
>
> On Wed, Mar 26, 2025 at 01:05:40PM -0700, Howard Chu wrote:
> > Changes in v2:
> > * Simplify the code (written by Namhyung)
>
> Please move this below "---" after S-o-b tags so that it can be ignored
> when applying.

Sorry I missed this, you mean this one before the diff stat?

---
tools/perf/builtin-trace.c | 16 +++++-----------
1 file changed, 5 insertions(+), 11 deletions(-)


>
> >
> > In my previous fix of runtime error(Link:
> > https://lore.kernel.org/linux-perf-users/20250122025519.361873-1-howardchu95@xxxxxxxxx/),
> > I made a mistake of decrementing one unconditionally, regardless of
> > whether an extra 'syscall_nr' or 'nr' field was present in
> > libtraceevent's tp_format. This may cause perf trace to allocate one
> > fewer arg_fmt entry than needed for the accurate representation of syscall
> > arguments.
> >
> > This patch corrects the mistake by checking the presence of'syscall_nr' or
> > 'nr', and adjusting the length of arg_fmt[] accordingly.
> >
> > Signed-off-by: Howard Chu <howardchu95@xxxxxxxxx>
> > Suggested-by: Namhyung Kim <namhyung@xxxxxxxxxx>
>
> Also please add the Fixes tag.

np.

Thanks,
Howard
>
> Thanks,
> Namhyung
>
> > ---
> >  tools/perf/builtin-trace.c | 16 +++++-----------
> >  1 file changed, 5 insertions(+), 11 deletions(-)
> >
> > diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
> > index a102748bd0c9..439e152186da 100644
> > --- a/tools/perf/builtin-trace.c
> > +++ b/tools/perf/builtin-trace.c
> > @@ -2022,9 +2022,6 @@ static int syscall__alloc_arg_fmts(struct syscall *sc, int nr_args)
> >  {
> >       int idx;
> >
> > -     if (nr_args == RAW_SYSCALL_ARGS_NUM && sc->fmt && sc->fmt->nr_args != 0)
> > -             nr_args = sc->fmt->nr_args;
> > -
> >       sc->arg_fmt = calloc(nr_args, sizeof(*sc->arg_fmt));
> >       if (sc->arg_fmt == NULL)
> >               return -1;
> > @@ -2034,7 +2031,6 @@ static int syscall__alloc_arg_fmts(struct syscall *sc, int nr_args)
> >                       sc->arg_fmt[idx] = sc->fmt->arg[idx];
> >       }
> >
> > -     sc->nr_args = nr_args;
> >       return 0;
> >  }
> >
> > @@ -2176,14 +2172,9 @@ static int syscall__read_info(struct syscall *sc, struct trace *trace)
> >               return err;
> >       }
> >
> > -     /*
> > -      * The tracepoint format contains __syscall_nr field, so it's one more
> > -      * than the actual number of syscall arguments.
> > -      */
> > -     if (syscall__alloc_arg_fmts(sc, sc->tp_format->format.nr_fields - 1))
> > -             return -ENOMEM;
> > -
> >       sc->args = sc->tp_format->format.fields;
> > +     sc->nr_args = sc->tp_format->format.nr_fields;
> > +
> >       /*
> >        * We need to check and discard the first variable '__syscall_nr'
> >        * or 'nr' that mean the syscall number. It is needless here.
> > @@ -2194,6 +2185,9 @@ static int syscall__read_info(struct syscall *sc, struct trace *trace)
> >               --sc->nr_args;
> >       }
> >
> > +     if (syscall__alloc_arg_fmts(sc, sc->nr_args))
> > +             return -ENOMEM;
> > +
> >       sc->is_exit = !strcmp(name, "exit_group") || !strcmp(name, "exit");
> >       sc->is_open = !strcmp(name, "open") || !strcmp(name, "openat");
> >
> > --
> > 2.45.2
> >