linux-kernel - Re: [RFC PATCH 1/7] tracing/probe: Check maxactive error cases

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Date:   Wed, 13 Mar 2019 23:37:39 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Tom Zanussi <zanussi@...nel.org>, tglx@...utronix.de,
        namhyung@...nel.org, bigeasy@...utronix.de, joel@...lfernandes.org,
        linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org
Subject: Re: [RFC PATCH 1/7] tracing/probe: Check maxactive error cases

On Wed, 13 Mar 2019 09:20:51 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Wed, 13 Mar 2019 21:27:42 +0900
> Masami Hiramatsu <mhiramat@...nel.org> wrote:
> 
> > Check maxactive on kprobe error case, because maxactive
> > is only for kretprobe, not for kprobe. Also, maxactive
> > should not be 0, it should be at least 1.
> > 
> > Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> > ---
> >  kernel/trace/trace_kprobe.c |   10 +++++++---
> >  1 file changed, 7 insertions(+), 3 deletions(-)
> > 
> > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> > index d5fb09ebba8b..d47e12596f12 100644
> > --- a/kernel/trace/trace_kprobe.c
> > +++ b/kernel/trace/trace_kprobe.c
> > @@ -624,7 +624,11 @@ static int trace_kprobe_create(int argc, const char *argv[])
> >  	if (event)
> >  		event++;
> >  
> > -	if (is_return && isdigit(argv[0][1])) {
> > +	if (isdigit(argv[0][1])) {
> > +		if (!is_return) {
> > +			pr_info("Maxactive is not for kprobe");
> 
> So now 'p1:..." will error out and not just be ignored?

Yes, I think it is better to tell user "your command has a
meaningless option, maybe you made a mistake" than ignore that.

Thank you,

> 
> -- Steve
> 
> > +			return -EINVAL;
> > +		}
> >  		if (event)
> >  			len = event - &argv[0][1] - 1;
> >  		else
> > @@ -634,8 +638,8 @@ static int trace_kprobe_create(int argc, const char *argv[])
> >  		memcpy(buf, &argv[0][1], len);
> >  		buf[len] = '\0';
> >  		ret = kstrtouint(buf, 0, &maxactive);
> > -		if (ret) {
> > -			pr_info("Failed to parse maxactive.\n");
> > +		if (ret || !maxactive) {
> > +			pr_info("Invalid maxactive number\n");
> >  			return ret;
> >  		}
> >  		/* kretprobes instances are iterated over via a list. The
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>