[PATCH 1/2] tracing: Add check for NULL event field when creating hist field

From: Tom Zanussi
Date: Mon Apr 25 2016 - 15:02:18 EST


Smatch flagged create_hist_field() as possibly being able to
dereference a NULL pointer, although the current code exits in all
cases where the event field could be NULL, so it's not actually a
problem.

Still, to prevent future changes to the code from overlooking new
cases, make the NULL pointer check explicit and warn once in that
case.

Signed-off-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
---
kernel/trace/trace_events_hist.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index f98b6b3..0c05b8a 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -371,6 +371,9 @@ static struct hist_field *create_hist_field(struct ftrace_event_field *field,
goto out;
}

+ if (WARN_ON_ONCE(!field))
+ goto out;
+
if (is_string_field(field)) {
flags |= HIST_FIELD_FL_STRING;

--
1.9.3