[PATCH 1/5] [BUGFIX] tracing: Returns -EBUSY when event_enable_funcfails to get module

From: Masami Hiramatsu
Date: Thu May 16 2013 - 07:51:36 EST

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.pt@xxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
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,
/* 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)

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/