[PATCH 3/3] perf ftrace: Handle NULL at write_tracing_file()

[Taeung Song <treeze.taeung@gmail.com>]

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@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Taeung Song <treeze.taeung@gmail.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