linux-kernel - Re: [PATCH] perf tools: avoid reading out of scope array

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Date:   Wed, 23 Oct 2019 10:29:12 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Ian Rogers <irogers@...gle.com>
Cc:     He Kuang <hekuang@...wei.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH] perf tools: avoid reading out of scope array

On Thu, Oct 17, 2019 at 10:05:31AM -0700, Ian Rogers wrote:
> Modify tracepoint name into 2 sys components and assemble at use. This
> avoids the sys_name array being out of scope at the point of use.
> Bug caught with LLVM's address sanitizer with fuzz generated input of
> ":cs\1" to parse_events.
> 
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
>  tools/perf/util/parse-events.y | 36 +++++++++++++++++++++++-----------
>  1 file changed, 25 insertions(+), 11 deletions(-)
> 
> diff --git a/tools/perf/util/parse-events.y b/tools/perf/util/parse-events.y
> index 48126ae4cd13..28be39a703c9 100644
> --- a/tools/perf/util/parse-events.y
> +++ b/tools/perf/util/parse-events.y
> @@ -104,7 +104,8 @@ static void inc_group_count(struct list_head *list,
>  	struct list_head *head;
>  	struct parse_events_term *term;
>  	struct tracepoint_name {
> -		char *sys;
> +		char *sys1;
> +		char *sys2;
>  		char *event;
>  	} tracepoint_name;
>  	struct parse_events_array array;
> @@ -425,9 +426,19 @@ tracepoint_name opt_event_config
>  	if (error)
>  		error->idx = @1.first_column;
>  
> -	if (parse_events_add_tracepoint(list, &parse_state->idx, $1.sys, $1.event,
> -					error, $2))
> -		return -1;
> +        if ($1.sys2) {
> +		char sys_name[128];
> +		snprintf(&sys_name, sizeof(sys_name), "%s-%s",
> +			$1.sys1, $1.sys2);
> +		if (parse_events_add_tracepoint(list, &parse_state->idx,
> +						sys_name, $1.event,
> +						error, $2))
> +			return -1;
> +        } else
> +		if (parse_events_add_tracepoint(list, &parse_state->idx,
> +						$1.sys1, $1.event,
> +						error, $2))
> +			return -1;

nice catch, please enclose all multiline condition legs with {}

other than that

Acked-by: Jiri Olsa <jolsa@...nel.org>

thanks,
jirka

>  
>  	$$ = list;
>  }
> @@ -435,19 +446,22 @@ tracepoint_name opt_event_config
>  tracepoint_name:
>  PE_NAME '-' PE_NAME ':' PE_NAME
>  {
> -	char sys_name[128];
> -	struct tracepoint_name tracepoint;
> -
> -	snprintf(&sys_name, 128, "%s-%s", $1, $3);
> -	tracepoint.sys = &sys_name;
> -	tracepoint.event = $5;
> +	struct tracepoint_name tracepoint = {
> +		.sys1 = $1,
> +		.sys2 = $3,
> +		.event = $5,
> +	};
>  
>  	$$ = tracepoint;
>  }
>  |
>  PE_NAME ':' PE_NAME
>  {
> -	struct tracepoint_name tracepoint = {$1, $3};
> +	struct tracepoint_name tracepoint = {
> +		.sys1 = $1,
> +		.sys2 = NULL,
> +		.event = $3,
> +	};
>  
>  	$$ = tracepoint;
>  }
> -- 
> 2.23.0.700.g56cf767bdb-goog
>