linux-kernel - Re: [PATCH v2 2/3] tracing: Fix parse_synth

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Date:   Thu, 01 Oct 2020 16:50:02 -0500
From:   Tom Zanussi <zanussi@...nel.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     rostedt@...dmis.org, axelrasmussen@...gle.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] tracing: Fix parse_synth_field() error handling

Hi Masami,

On Thu, 2020-10-01 at 14:27 +0900, Masami Hiramatsu wrote:
> Hi Tom,
> 
> On Wed, 30 Sep 2020 13:40:51 -0500
> Tom Zanussi <zanussi@...nel.org> wrote:
> 
> > synth_field_size() returns either a positive size or an error (zero
> > or
> > a negative value). However, the existing code assumes the only
> > error
> > value is 0. It doesn't handle negative error codes, as it assigns
> > directly to field->size (a size_t; unsigned), thereby interpreting
> > the
> > error code as a valid size instead.
> > 
> > Do the test before assignment to field->size.
> 
> This looks good to me. And I guess it is a kind of bugfix which
> should be backported?
> (doesn't this need a Fixes tag?)

Yep, thanks for pointing that out.

> 
> Reviewed-by: Masami Hiramatsu <mhiramat@...nel.org>
> 

Thanks!

Tom

> Thank you,
> 
> > 
> > [ axelrasmussen@...gle.com: changelog addition, first paragraph
> > above ]
> > 
> > Signed-off-by: Tom Zanussi <zanussi@...nel.org>
> > ---
> >  kernel/trace/trace_events_synth.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> > 
> > diff --git a/kernel/trace/trace_events_synth.c
> > b/kernel/trace/trace_events_synth.c
> > index a9cd7793f7ea..fa8a99828f41 100644
> > --- a/kernel/trace/trace_events_synth.c
> > +++ b/kernel/trace/trace_events_synth.c
> > @@ -465,6 +465,7 @@ static struct synth_field
> > *parse_synth_field(int argc, const char **argv,
> >  	struct synth_field *field;
> >  	const char *prefix = NULL, *field_type = argv[0], *field_name,
> > *array;
> >  	int len, ret = 0;
> > +	ssize_t size;
> >  
> >  	if (field_type[0] == ';')
> >  		field_type++;
> > @@ -520,11 +521,12 @@ static struct synth_field
> > *parse_synth_field(int argc, const char **argv,
> >  			field->type[len - 1] = '\0';
> >  	}
> >  
> > -	field->size = synth_field_size(field->type);
> > -	if (!field->size) {
> > +	size = synth_field_size(field->type);
> > +	if (size <= 0) {
> >  		ret = -EINVAL;
> >  		goto free;
> >  	}
> > +	field->size = size;
> >  
> >  	if (synth_field_is_string(field->type))
> >  		field->is_string = true;
> > -- 
> > 2.17.1
> > 
> 
>