trace-cmd library: Do not call callbacks with NULL record

Commit Message

Steven Rostedt Oct. 7, 2022, 6:38 p.m. UTC

From: "Steven Rostedt (Google)" <[e-mail]>

The callbacks path can possibly be called when the next record is NULL. Do
not call the callbacks in this case, as they are not expecting a NULL
record, nor should they have to.

Move the code that calls the callbacks in tracecmd_iterate_events() and
tracecmd_iterate_events_multi() into a single helper function to alleviate
fixing one and not the other.

Reported-by: Ian Rogers <[e-mail]>
Fixes: 3cd1b55f3 ("trace-cmd library: Add tracecmd_follow_event()")
Fixes: 82ed4a937 ("trace-cmd library: Add filtering logic for iterating events")
Signed-off-by: Steven Rostedt (Google) <[e-mail]>
---
 lib/trace-cmd/trace-input.c | 42 ++++++++++++++++++++++++-------------
 1 file changed, 28 insertions(+), 14 deletions(-)

Patch

diff --git a/lib/trace-cmd/trace-input.c b/lib/trace-cmd/trace-input.c
index d81918249871..6a8ca2e8a6b8 100644
--- a/lib/trace-cmd/trace-input.c
+++ b/lib/trace-cmd/trace-input.c
@@ -2648,6 +2648,29 @@  static int call_followers(struct tracecmd_input *handle,
 	return ret;
 }
 
+static int call_callbacks(struct tracecmd_input *handle, struct tep_record *record,
+			  int next_cpu,
+			  int (*callback)(struct tracecmd_input *handle,
+					  struct tep_record *,
+					  int, void *),
+			  void *callback_data)
+{
+	int ret = 0;
+
+	if (!record)
+		return 0;
+
+	if (!handle->filter ||
+	    tracecmd_filter_match(handle->filter, record) == TRACECMD_FILTER_MATCH) {
+		if (handle->nr_followers)
+			ret = call_followers(handle, record, next_cpu);
+		if (!ret && callback)
+			ret = callback(handle, record, next_cpu, callback_data);
+	}
+
+	return ret;
+}
+
 /**
  * tracecmd_iterate_events - iterate events over a given handle
  * @handle: The handle to iterate over
@@ -2709,13 +2732,9 @@  int tracecmd_iterate_events(struct tracecmd_input *handle,
 			record = tracecmd_read_data(handle, next_cpu);
 			records[next_cpu] = tracecmd_peek_data(handle, next_cpu);
 
-			if (!handle->filter ||
-			    tracecmd_filter_match(handle->filter, record) == TRACECMD_FILTER_MATCH) {
-				if (handle->nr_followers)
-					ret = call_followers(handle, record, next_cpu);
-				if (!ret && callback)
-					ret = callback(handle, record, next_cpu, callback_data);
-			}
+			ret = call_callbacks(handle, record, next_cpu,
+					     callback, callback_data);
+
 			tracecmd_free_record(record);
 		}
 	} while (next_cpu >= 0 && ret >= 0);
@@ -2803,14 +2822,9 @@  int tracecmd_iterate_events_multi(struct tracecmd_input **handles,
 			record = tracecmd_read_data(handle, cpu);
 			records[next_cpu].record = tracecmd_peek_data(handle, cpu);
 
-			if (!handle->filter ||
-			    tracecmd_filter_match(handle->filter, record) == TRACECMD_FILTER_MATCH) {
-				if (handle->nr_followers)
-					ret = call_followers(handle, record, next_cpu);
+			ret = call_callbacks(handle, record, next_cpu,
+					     callback, callback_data);
 
-				if (!ret && callback)
-					ret = callback(handle, record, next_cpu, callback_data);
-			}
 			tracecmd_free_record(record);
 		}