[tip:perf/core] tools lib traceevent: Add sanity check to is_timestamp_in_us()

[tip-bot for Tzvetomir Stoyanov <tipbot@zytor.com>]

Commit-ID:  44e92f8389b2242efde77d5321ffa88decd47df6
Gitweb:     https://git.kernel.org/tip/44e92f8389b2242efde77d5321ffa88decd47df6
Author:     Tzvetomir Stoyanov <tstoyanov@vmware.com>
AuthorDate: Wed, 28 Nov 2018 14:55:52 -0500
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Mon, 17 Dec 2018 14:55:19 -0300

tools lib traceevent: Add sanity check to is_timestamp_in_us()

This patch adds a sanity check to is_timestamp_in_us() input parameter
trace_clock. It avoids a potential segfault in this function for the
case trace_clock is NULL.

Reported-by: Slavomir Kaslev <kaslevs@vmware.com>
Signed-off-by: Tzvetomir Stoyanov <tstoyanov@vmware.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/20181128145552.68c4f87b@gandalf.local.home
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/lib/traceevent/event-parse.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
index fbd6d6813fab..2b5cb33046ce 100644
--- a/tools/lib/traceevent/event-parse.c
+++ b/tools/lib/traceevent/event-parse.c
@@ -5409,7 +5409,7 @@ void tep_event_info(struct trace_seq *s, struct tep_event_format *event,
 
 static bool is_timestamp_in_us(char *trace_clock, bool use_trace_clock)
 {
-	if (!use_trace_clock)
+	if (!trace_clock || !use_trace_clock)
 		return true;
 
 	if (!strcmp(trace_clock, "local") || !strcmp(trace_clock, "global")