linux-kernel - Re: [PATCH 2/2] tracing/probes: Fix to exit fetching if an error is detected

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Date:   Sun, 2 Jul 2023 22:46:54 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Dan Carpenter <dan.carpenter@...aro.org>,
        linux-trace-kernel@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] tracing/probes: Fix to exit fetching if an error is
 detected

On Sat, 1 Jul 2023 21:16:17 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Thu, 29 Jun 2023 23:13:46 +0900
> "Masami Hiramatsu (Google)" <mhiramat@...nel.org> wrote:
> 
> > From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> > 
> > Fix to exit fetching arguments if an error is detected when storing
> > strings. Without this fix, if an array is specified with string types
> > it may point wrong address to store the data.
> 
>   "it may store that data at the wrong address".

Good catch! Yes, while updating the data location, the remaining length
and offset becomes wrong and next array element (string) will be stored
in wrong memory address.

> 
> > 
> > Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
> > Closes: https://lore.kernel.org/all/8819b154-2ba1-43c3-98a2-cbde20892023@moroto.mountain/
> > Fixes: 9b960a38835f ("tracing: probeevent: Unify fetch_insn processing common part")
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> > ---
> >  kernel/trace/trace_probe_tmpl.h |    2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/kernel/trace/trace_probe_tmpl.h b/kernel/trace/trace_probe_tmpl.h
> > index 4735c5cb76fa..d6f2bf69f9bc 100644
> > --- a/kernel/trace/trace_probe_tmpl.h
> > +++ b/kernel/trace/trace_probe_tmpl.h
> > @@ -193,6 +193,8 @@ process_fetch_insn_bottom(struct fetch_insn *code, unsigned long val,
> >  	default:
> >  		return -EILSEQ;
> >  	}
> > +	if (ret < 0)
> > +		return ret;
> 
> Reviewed-by: Steven Rostedt (Google) <rostedt@...dmis.org>

Thanks!

> 
> -- Steve
> 
> >  	code++;
> >  
> >  	/* 4th stage: modify stored value if needed */
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>