linux-kernel - Re: [PATCH v1 06/11] perf hists: Smatch: Fix potential NULL pointer dereference

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Message-ID: <20190702110728.GA15322@krava>
Date:   Tue, 2 Jul 2019 13:07:28 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Leo Yan <leo.yan@...aro.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Andi Kleen <ak@...ux.intel.com>,
        "David S. Miller" <davem@...emloft.net>,
        Davidlohr Bueso <dave@...olabs.net>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Jin Yao <yao.jin@...ux.intel.com>,
        Song Liu <songliubraving@...com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Alexios Zavras <alexios.zavras@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Changbin Du <changbin.du@...el.com>,
        Eric Saint-Etienne <eric.saint.etienne@...cle.com>,
        Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        Thomas Richter <tmricht@...ux.ibm.com>,
        Alexey Budankov <alexey.budankov@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v1 06/11] perf hists: Smatch: Fix potential NULL pointer
 dereference

On Tue, Jul 02, 2019 at 06:34:15PM +0800, Leo Yan wrote:
> Based on the following report from Smatch, fix the potential
> NULL pointer dereference check.
> 
>   tools/perf/ui/browsers/hists.c:641
>   hist_browser__run() error: we previously assumed 'hbt' could be
>   null (see line 625)
> 
>   tools/perf/ui/browsers/hists.c:3088
>   perf_evsel__hists_browse() error: we previously assumed
>   'browser->he_selection' could be null (see line 2902)
> 
>   tools/perf/ui/browsers/hists.c:3272
>   perf_evsel_menu__run() error: we previously assumed 'hbt' could be
>   null (see line 3260)
> 
> This patch firstly validating the pointers before access them, so can
> fix potential NULL pointer dereference.
> 
> Signed-off-by: Leo Yan <leo.yan@...aro.org>
> ---
>  tools/perf/ui/browsers/hists.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/perf/ui/browsers/hists.c b/tools/perf/ui/browsers/hists.c
> index 3421ecbdd3f0..2ba33040ddd8 100644
> --- a/tools/perf/ui/browsers/hists.c
> +++ b/tools/perf/ui/browsers/hists.c
> @@ -638,7 +638,9 @@ int hist_browser__run(struct hist_browser *browser, const char *help,
>  		switch (key) {
>  		case K_TIMER: {

not sure this can really happen, perhaps WARN_ON_ONCE(!hbt) would be
good in here

jirka

>  			u64 nr_entries;
> -			hbt->timer(hbt->arg);
> +
> +			if (hbt)
> +				hbt->timer(hbt->arg);
>  
>  			if (hist_browser__has_filter(browser) ||
>  			    symbol_conf.report_hierarchy)

SNIP