linux-kernel - Re: [PATCH] perf trace: Fix potential USE_AFTER

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Date:   Thu, 14 Feb 2019 09:34:11 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Bo YU <tsu.yubo@...il.com>
Cc:     peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        alexander.shishkin@...ux.intel.com, namhyung@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf trace: Fix potential USE_AFTER_FREE  problem

On Thu, Feb 14, 2019 at 12:23:56AM -0500, Bo YU wrote:
> From: Bo Yu <tsu.yubo@...il.com>
> 
> There is a freed pointer "evsel", so fix it.
> 
> Detected by CoverityScan, CID#1442595("Memory-illegalaccesses
> (USE_AFTER_FREE)")
> Fixes: 6ab3bc240ade4("perf trace: Support multiple "vfs_getname" probes")
> 
> Signed-off-by: Bo Yu <tsu.yubo@...il.com>
> ---
>  tools/perf/builtin-trace.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
> index b36061cd1ab8..4036b20a1067 100644
> --- a/tools/perf/builtin-trace.c
> +++ b/tools/perf/builtin-trace.c
> @@ -2515,7 +2515,7 @@ static size_t trace__fprintf_thread_summary(struct trace *trace, FILE *fp);
>  static bool perf_evlist__add_vfs_getname(struct perf_evlist *evlist)
>  {
>  	bool found = false;
> -	struct perf_evsel *evsel, *tmp;
> +	struct perf_evsel *evsel = NULL, *tmp;

hum, I can't see how this change could matter,
could you pelase explain?

jirka

>  	struct parse_events_error err = { .idx = 0, };
>  	int ret = parse_events(evlist, "probe:vfs_getname*", &err);
>  
> -- 
> 2.11.0
>