[PATCH 3/4] tracing/profile: fix profile_disable vs module_unload

[Steven Rostedt]

From: Li Zefan <lizf@xxxxxxxxxxxxxx>

If the correspoding module is unloaded before ftrace_profile_disable()
is called, event->profile_disable() won't be called, which can
cause oops:

  # insmod trace-events-sample.ko
  # perf record -f -a -e sample:foo_bar sleep 3 &
  # sleep 1
  # rmmod trace_events_sample
  # insmod trace-events-sample.ko
  OOPS!

Signed-off-by: Li Zefan <lizf@xxxxxxxxxxxxxx>
LKML-Reference: <4A9214E3.2070807@xxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 kernel/trace/trace_event_profile.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/kernel/trace/trace_event_profile.c b/kernel/trace/trace_event_profile.c
index 11ba5bb..55a25c9 100644
--- a/kernel/trace/trace_event_profile.c
+++ b/kernel/trace/trace_event_profile.c
@@ -5,6 +5,7 @@
  *
  */
 
+#include <linux/module.h>
 #include "trace.h"
 
 int ftrace_profile_enable(int event_id)
@@ -14,7 +15,8 @@ int ftrace_profile_enable(int event_id)
 
 	mutex_lock(&event_mutex);
 	list_for_each_entry(event, &ftrace_events, list) {
-		if (event->id == event_id && event->profile_enable) {
+		if (event->id == event_id && event->profile_enable &&
+		    try_module_get(event->mod)) {
 			ret = event->profile_enable(event);
 			break;
 		}
@@ -32,6 +34,7 @@ void ftrace_profile_disable(int event_id)
 	list_for_each_entry(event, &ftrace_events, list) {
 		if (event->id == event_id) {
 			event->profile_disable(event);
+			module_put(event->mod);
 			break;
 		}
 	}
-- 
1.6.3.3

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