[PATCH] perf parse-events: add defensive null check

From: Ian Rogers <irogers@google.com>
To: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	John Garry <john.garry@huawei.com>,
	Jin Yao <yao.jin@linux.intel.com>,
	Andi Kleen <ak@linux.intel.com>,
	Kan Liang <kan.liang@linux.intel.com>,
	linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com
Cc: Stephane Eranian <eranian@google.com>, Ian Rogers <irogers@google.com>
Subject: [PATCH] perf parse-events: add defensive null check
Date: Wed, 25 Mar 2020 09:40:22 -0700	[thread overview]
Message-ID: <20200325164022.41385-1-irogers@google.com> (raw)

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>
---
 tools/perf/util/pmu.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index 616fbda7c3fc..ef6a63f3d386 100644
--- 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;
 		}
 	}
 
-- 
2.25.1.696.g5e7596f4ac-goog

