[tip:perf/urgent] perf top: Fix potential NULL pointer dereference detected by the smatch tool

[tip-bot for Leo Yan]

Commit-ID:  111442cfc8abdeaa7ec1407f07ef7b3e5f76654e
Gitweb:     https://git.kernel.org/tip/111442cfc8abdeaa7ec1407f07ef7b3e5f76654e
Author:     Leo Yan <leo.yan@xxxxxxxxxx>
AuthorDate: Tue, 2 Jul 2019 18:34:12 +0800
Committer:  Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Tue, 9 Jul 2019 09:33:54 -0300

perf top: Fix potential NULL pointer dereference detected by the smatch tool

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@xxxxxxxxxx>
Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Alexey Budankov <alexey.budankov@xxxxxxxxxxxxxxx>
Cc: Alexios Zavras <alexios.zavras@xxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Changbin Du <changbin.du@xxxxxxxxx>
Cc: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Cc: Eric Saint-Etienne <eric.saint.etienne@xxxxxxxxxx>
Cc: Jin Yao <yao.jin@xxxxxxxxxxxxxxx>
Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Cc: Song Liu <songliubraving@xxxxxx>
Cc: Suzuki Poulouse <suzuki.poulose@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Thomas Richter <tmricht@xxxxxxxxxxxxx>
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/20190702103420.27540-4-leo.yan@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 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 6d40a4ef58c5..b46b3c9f57a0 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -101,7 +101,7 @@ 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;
@@ -110,6 +110,8 @@ 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;
 
@@ -226,7 +228,7 @@ 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;
@@ -234,6 +236,8 @@ 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);