perf parse-events: Add defensive NULL check

Terms may have a NULL config in which case a strcmp will SEGV. This can
be reproduced with:

  perf stat -e '*/event=?,nr/' sleep 1

Add a NULL check to avoid this. This was caught by LLVM's libfuzzer.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: John Garry <john.garry@huawei.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: clang-built-linux@googlegroups.com
Link: http://lore.kernel.org/lkml/20200325164022.41385-1-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index 616fbda..ef6a63f 100644 (file)
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -984,12 +984,11 @@ static int pmu_resolve_param_term(struct parse_events_term *term,
        struct parse_events_term *t;
 
        list_for_each_entry(t, head_terms, list) {
-               if (t->type_val == PARSE_EVENTS__TERM_TYPE_NUM) {
-                       if (!strcmp(t->config, term->config)) {
-                               t->used = true;
-                               *value = t->val.num;
-                               return 0;
-                       }
+               if (t->type_val == PARSE_EVENTS__TERM_TYPE_NUM &&
+                   t->config && !strcmp(t->config, term->config)) {
+                       t->used = true;
+                       *value = t->val.num;
+                       return 0;
                }
        }