[PATCH] trace-cmd Library: Update record after callback in iterators

[Steven Rostedt <rostedt@goodmis.org>]

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

The function graph plugin will look at the next event and may even
increment it if it is a leaf function. The current iterators update the
next record before the callback. This leaves them vulnerable to
corruption if the callback updates to the next record like function
graph plugin does.

Peek at the next record after the callback to ensure that the next
record is the one that will be used for the next iterator.

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 lib/trace-cmd/trace-input.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/trace-cmd/trace-input.c b/lib/trace-cmd/trace-input.c
index aa54e7fa..594eb74a 100644
--- a/lib/trace-cmd/trace-input.c
+++ b/lib/trace-cmd/trace-input.c
@@ -2810,11 +2810,11 @@ int tracecmd_iterate_events(struct tracecmd_input *handle,
 		if (next_cpu >= 0) {
 			/* Need to call read_data to increment to the next record */
 			record = tracecmd_read_data(handle, next_cpu);
-			records[next_cpu] = tracecmd_peek_data(handle, next_cpu);
 
 			ret = call_callbacks(handle, record, next_cpu,
 					     callback, callback_data);
 
+			records[next_cpu] = tracecmd_peek_data(handle, next_cpu);
 			tracecmd_free_record(record);
 		}
 	} while (next_cpu >= 0 && ret >= 0);
@@ -2900,12 +2900,12 @@ int tracecmd_iterate_events_multi(struct tracecmd_input **handles,
 			cpu = next_cpu - handle->start_cpu;
 			/* Need to call read_data to increment to the next record */
 			record = tracecmd_read_data(handle, cpu);
-			records[next_cpu].record = tracecmd_peek_data(handle, cpu);
 
 			ret = call_callbacks(handle, record, next_cpu,
 					     callback, callback_data);
 
 			tracecmd_free_record(record);
+			records[next_cpu].record = tracecmd_peek_data(handle, cpu);
 		}
 
 	} while (next_cpu >= 0 && ret >= 0);
-- 
2.35.1