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

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Date:   Thu, 4 Feb 2021 00:08:14 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Jianlin Lv <Jianlin.Lv@....com>
Cc:     peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        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

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>

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>