linux-kernel - [PATCH v1 03/11] perf top: Smatch: Fix potential NULL pointer dereference

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Date:   Tue,  2 Jul 2019 18:34:12 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.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
Cc:     Leo Yan <leo.yan@...aro.org>
Subject: [PATCH v1 03/11] perf top: Smatch: Fix potential NULL pointer dereference

Based on the following report from Smatch, fix the potential
NULL pointer dereference check.

  tools/perf/builtin-top.c:109
  perf_top__parse_source() warn: variable dereferenced before check 'he'
  (see line 103)

  tools/perf/builtin-top.c:233
  perf_top__show_details() warn: variable dereferenced before check 'he'
  (see line 228)

tools/perf/builtin-top.c
101 static int perf_top__parse_source(struct perf_top *top, struct hist_entry *he)
102 {
103         struct perf_evsel *evsel = hists_to_evsel(he->hists);
                                                      ^^^^
104         struct symbol *sym;
105         struct annotation *notes;
106         struct map *map;
107         int err = -1;
108
109         if (!he || !he->ms.sym)
110                 return -1;

This patch moves the values assignment after validating pointer 'he'.

Signed-off-by: Leo Yan <leo.yan@...aro.org>
---
 tools/perf/builtin-top.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 12b6b15a9675..13234c322981 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -100,7 +100,7 @@ static void perf_top__resize(struct perf_top *top)
 
 static int perf_top__parse_source(struct perf_top *top, struct hist_entry *he)
 {
-	struct perf_evsel *evsel = hists_to_evsel(he->hists);
+	struct perf_evsel *evsel;
 	struct symbol *sym;
 	struct annotation *notes;
 	struct map *map;
@@ -109,6 +109,8 @@ static int perf_top__parse_source(struct perf_top *top, struct hist_entry *he)
 	if (!he || !he->ms.sym)
 		return -1;
 
+	evsel = hists_to_evsel(he->hists);
+
 	sym = he->ms.sym;
 	map = he->ms.map;
 
@@ -225,7 +227,7 @@ static void perf_top__record_precise_ip(struct perf_top *top,
 static void perf_top__show_details(struct perf_top *top)
 {
 	struct hist_entry *he = top->sym_filter_entry;
-	struct perf_evsel *evsel = hists_to_evsel(he->hists);
+	struct perf_evsel *evsel;
 	struct annotation *notes;
 	struct symbol *symbol;
 	int more;
@@ -233,6 +235,8 @@ static void perf_top__show_details(struct perf_top *top)
 	if (!he)
 		return;
 
+	evsel = hists_to_evsel(he->hists);
+
 	symbol = he->ms.sym;
 	notes = symbol__annotation(symbol);
 
-- 
2.17.1