[PATCH] racing/user_events: Prevent same address and bit per process

[sunliming]

User processes register name_args for events. If the same name are registered
multiple times in the same process, it can cause undefined behavior. Because
the same name may be used for a diffrent event. If this event has the same
format as the original event, it is impossible to distinguish the trace output
of these two events. If the event has a different format from the original event,
the trace output of the new event is incorrect.

Return EADDRINUSE back to the user process if the same event has being registered
in the same process.

Signed-off-by: sunliming <sunliming@xxxxxxxxxx>
---
 kernel/trace/trace_events_user.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
index b1ecd7677642..4ef6bdb5c07c 100644
--- a/kernel/trace/trace_events_user.c
+++ b/kernel/trace/trace_events_user.c
@@ -1996,7 +1996,7 @@ static int user_events_ref_add(struct user_event_file_info *info,
 
 		for (i = 0; i < count; ++i)
 			if (refs->events[i] == user)
-				return i;
+				return -EADDRINUSE;
 	}
 
 	size = struct_size(refs, events, count + 1);
-- 
2.25.1