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

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Message-Id: <20200325164022.41385-1-irogers@google.com>
Date:   Wed, 25 Mar 2020 09:40:22 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        John Garry <john.garry@...wei.com>,
        Jin Yao <yao.jin@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com
Cc:     Stephane Eranian <eranian@...gle.com>,
        Ian Rogers <irogers@...gle.com>
Subject: [PATCH] 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@...gle.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