linux-kernel - Re: [PATCH] [perf] sort : Fix null pointer dereference in _hist_entry__sym

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Date:   Thu, 18 Jun 2020 07:13:49 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Gaurav Singh <gaurav1086@...il.com>
Cc:     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>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>,
        "open list:PERFORMANCE EVENTS SUBSYSTEM" 
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] [perf] sort : Fix null pointer dereference in
 _hist_entry__sym_snprintf

> diff --git a/tools/perf/util/sort.c b/tools/perf/util/sort.c
> index d42339df20f8..25c7c96893f6 100644
> --- a/tools/perf/util/sort.c
> +++ b/tools/perf/util/sort.c
> @@ -294,6 +294,9 @@ static int _hist_entry__sym_snprintf(struct map_symbol *ms,
>  				     u64 ip, char level, char *bf, size_t size,
>  				     unsigned int width)
>  {
> +	if (!ms) 
> +		return 0;
> +
>  	struct symbol *sym = ms->sym;
>  	struct map *map = ms->map;
>  	size_t ret = 0;

This should have given warnings because Linux and perf coding style
forbids fixed statement/declarations.

Also what's the backtrace where it is NULL? Perhaps better to fix it in
the caller.

-Andi