linux-kernel - Re: [PATCH v2] perf probe: Added protection to avoid endless loop

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Date:   Wed, 3 Feb 2021 13:22:58 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Jianlin Lv <Jianlin.Lv@....com>, peterz@...radead.org,
        mingo@...hat.com, mark.rutland@....com,
        alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
        namhyung@...nel.org, srikar@...ux.vnet.ibm.com,
        adrian.hunter@...el.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] perf probe: Added protection to avoid endless loop

Em Thu, Feb 04, 2021 at 12:08:14AM +0900, Masami Hiramatsu escreveu:
> On Wed,  3 Feb 2021 22:57:02 +0800
> Jianlin Lv <Jianlin.Lv@....com> wrote:
> 
> > if dwarf_offdie() return NULL, the continue statement forces the next
> > iteration of the loop without update variable off. It will cause an
> > endless loop in the process of traversing the compilation unit.
> > So added exception protection for loop CUs.
> > 
> 
> Thanks for the quick update!
> 
> Acked-by: Masami Hiramatsu <mhiramat@...nel.org>

Thanks, applied.

- Arnaldo

 
> Thank you,
> 
> > Signed-off-by: Jianlin Lv <Jianlin.Lv@....com>
> > ---
> > v2: removed the statement that updates variable in the function argument.
> > ---
> >  tools/perf/util/probe-finder.c | 8 ++++++--
> >  1 file changed, 6 insertions(+), 2 deletions(-)
> > 
> > diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
> > index 76dd349aa48d..1b118c9c86a6 100644
> > --- a/tools/perf/util/probe-finder.c
> > +++ b/tools/perf/util/probe-finder.c
> > @@ -1187,8 +1187,10 @@ static int debuginfo__find_probe_location(struct debuginfo *dbg,
> >  	while (!dwarf_nextcu(dbg->dbg, off, &noff, &cuhl, NULL, NULL, NULL)) {
> >  		/* Get the DIE(Debugging Information Entry) of this CU */
> >  		diep = dwarf_offdie(dbg->dbg, off + cuhl, &pf->cu_die);
> > -		if (!diep)
> > +		if (!diep) {
> > +			off = noff;
> >  			continue;
> > +		}
> >  
> >  		/* Check if target file is included. */
> >  		if (pp->file)
> > @@ -1949,8 +1951,10 @@ int debuginfo__find_line_range(struct debuginfo *dbg, struct line_range *lr)
> >  
> >  		/* Get the DIE(Debugging Information Entry) of this CU */
> >  		diep = dwarf_offdie(dbg->dbg, off + cuhl, &lf.cu_die);
> > -		if (!diep)
> > +		if (!diep) {
> > +			off = noff;
> >  			continue;
> > +		}
> >  
> >  		/* Check if target file is included. */
> >  		if (lr->file)
> > -- 
> > 2.25.1
> > 
> 
> 
> -- 
> Masami Hiramatsu <mhiramat@...nel.org>

-- 

- Arnaldo