linux-kernel - Re: [PATCH] tracing: react to error return from traceprobe_parse_event

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Date:   Thu, 11 Aug 2022 09:20:52 +0200
From:   Lukas Bulwahn <lukas.bulwahn@...il.com>
To:     Linyu Yuan <quic_linyyuan@...cinc.com>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Tom Zanussi <zanussi@...nel.org>,
        kernel-janitors <kernel-janitors@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tracing: react to error return from traceprobe_parse_event_name()

On Thu, Aug 11, 2022 at 1:29 AM Linyu Yuan <quic_linyyuan@...cinc.com> wrote:
>
> hi Lukas,
>
> On 8/10/2022 11:09 PM, Lukas Bulwahn wrote:
> > The function traceprobe_parse_event_name() may set the first two function
> > arguments to a non-null value and still return -EINVAL to indicate an
> > unsuccessful completion of the function. Hence, it is not sufficient to
> > just check the result of the two function arguments for being not null,
> > but the return value also needs to be checked.
> >
> > Commit 95c104c378dc ("tracing: Auto generate event name when creating a
> > group of events") changed the error-return-value checking of the second
> > traceprobe_parse_event_name() invocation in __trace_eprobe_create() and
> > removed checking the return value to jump to the error handling case.
> >
> > Reinstate using the return value in the error-return-value checking.
> >
> > Signed-off-by: Lukas Bulwahn <lukas.bulwahn@...il.com>
> > ---
> >   kernel/trace/trace_eprobe.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c
> > index 4a0e9d927443..460d3ec8a256 100644
> > --- a/kernel/trace/trace_eprobe.c
> > +++ b/kernel/trace/trace_eprobe.c
> > @@ -883,7 +883,7 @@ static int __trace_eprobe_create(int argc, const char *argv[])
> >       trace_probe_log_set_index(1);
> >       sys_event = argv[1];
> >       ret = traceprobe_parse_event_name(&sys_event, &sys_name, buf2, 0);
> > -     if (!sys_event || !sys_name) {
> > +     if (!ret || !sys_event || !sys_name) {
>
> that's right, miss case sys_event and sys_name are not null, but invalid.
>
> it should be  if (ret || ...)  ?
>

Linyu, you are right. The visual symmetry tricked me into believing
the line above was right, but it is clearly wrong if you think about
it and look at the other invocation.

I send out a corrected patch v2:

https://lore.kernel.org/all/20220811071734.20700-1-lukas.bulwahn@gmail.com/

Please review, ack and pick the patch v2. Thanks.

Lukas