linux-kernel - [PATCH 3/3] perf ftrace: Handle NULL at write_tracing

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Date:   Thu, 26 Jan 2017 18:35:39 +0900
From:   Taeung Song <treeze.taeung@...il.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Wang Nan <wangnan0@...wei.com>,
        Taeung Song <treeze.taeung@...il.com>
Subject: [PATCH 3/3] perf ftrace: Handle NULL at write_tracing_file()

If a value for tracing file is NULL,
segment fault error can occur using strlen().
Of course, currently the function don't be given NULL value.
But write_tracing_file() can be generally used.
So add the if statement.

Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Namhyung Kim <namhyung@...nel.org>
Signed-off-by: Taeung Song <treeze.taeung@...il.com>
---
 tools/perf/builtin-ftrace.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index 8df5416..0754dee 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -54,8 +54,12 @@ static int write_tracing_file(const char *name, const char *val)
 {
 	char *file;
 	int fd, ret = -1;
-	ssize_t size = strlen(val);
+	ssize_t size;
 
+	if (val == NULL)
+		return -1;
+
+	size = strlen(val);
 	file = get_tracing_file(name);
 	if (!file) {
 		pr_debug("cannot get tracing file: %s\n", name);
-- 
2.7.4