linux-kernel - Re: [PATCH 1/2] tracing/probes: Fix to avoid double count of the string length on the array

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Message-Id: <20230702215623.fbdfa8f3a01a3d2ab9a6fa58@kernel.org>
Date:   Sun, 2 Jul 2023 21:56:23 +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 1/2] tracing/probes: Fix to avoid double count of the
 string length on the array

On Sat, 1 Jul 2023 21:08:40 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Thu, 29 Jun 2023 23:13:37 +0900
> "Masami Hiramatsu (Google)" <mhiramat@...nel.org> wrote:
> 
> > From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> > 
> > If there is an array is specified with the ustring or symstr, the length of
> 
>  "If there is an array specified with ustring or .." or "If an array is specified with ustring"
> 
> I prefer the latter.
> 
> > the strings are accumlated on both of 'ret' and 'total', which means the
> > length is double counted.
> > Just set the length to the 'ret' value to aviud double count.
> 
> 					"avoid"
> 
> > 
> > Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
> > Closes: https://lore.kernel.org/all/8819b154-2ba1-43c3-98a2-cbde20892023@moroto.mountain/
> > Fixes: 88903c464321 ("tracing/probe: Add ustring type for user-space string")
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> > ---
> >  kernel/trace/trace_probe_tmpl.h |    4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/kernel/trace/trace_probe_tmpl.h b/kernel/trace/trace_probe_tmpl.h
> > index 00707630788d..4735c5cb76fa 100644
> > --- a/kernel/trace/trace_probe_tmpl.h
> > +++ b/kernel/trace/trace_probe_tmpl.h
> > @@ -156,11 +156,11 @@ process_fetch_insn_bottom(struct fetch_insn *code, unsigned long val,
> >  			code++;
> >  			goto array;
> >  		case FETCH_OP_ST_USTRING:
> > -			ret += fetch_store_strlen_user(val + code->offset);
> > +			ret = fetch_store_strlen_user(val + code->offset);
> >  			code++;
> >  			goto array;
> >  		case FETCH_OP_ST_SYMSTR:
> > -			ret += fetch_store_symstrlen(val + code->offset);
> > +			ret = fetch_store_symstrlen(val + code->offset);
> 
> Other than the above,
> 
> Reviewed-by: Steven Rostedt (Google) <rostedt@...dmis.org>

Thanks! I'll resend it with fixes.

> 
> -- Steve
> 
> 
> >  			code++;
> >  			goto array;
> >  		default:
> 


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