Since try_module_get returns false( = 0) when it fails to
pindown a module, event_enable_func() returns 0 which means
"succeed". This can cause a kernel panic when the entry
is removed, because the event is already released.
This fixes the bug by returning -EBUSY, because the reason
why it fails is under removing module at that time.
Signed-off-by: Masami Hiramatsu <masami.hiramatsu...@hitachi.com>
Cc: Steven Rostedt <rost...@goodmis.org>
Cc: Frederic Weisbecker <fweis...@gmail.com>
Cc: Ingo Molnar <mi...@redhat.com>
---
kernel/trace/trace_events.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 7a0cf68..27963e2 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -2072,8 +2072,10 @@ event_enable_func(struct ftrace_hash *hash,
out_reg:
/* Don't let event modules unload while probe registered */
ret = try_module_get(file->event_call->mod);
- if (!ret)
+ if (!ret) {
+ ret = -EBUSY;
goto out_free;
+ }
ret = __ftrace_event_enable_disable(file, 1, 1);
if (ret < 0)
--
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