trace_module_add_events() ignores the return value of __register_event()
and unconditionally calls __add_event_to_tracers() for each event.
If __register_event() fails (for example, if event_init() fails), the
trace_event_call is not added to ftrace_events list, but
__add_event_to_tracers() still creates a trace_event_file pointing to it.
If module loading subsequently fails and module memory is freed, tracing
state retains a stale trace_event_call pointer in trace_event_file,
leading to a use-after-free when tracefs or tracing subsystem operations
are later executed.
Fix this by checking the return value of __register_event() and only
calling __add_event_to_tracers() if event registration succeeded.
Fixes: ae63b31e4d ("tracing: Separate out trace events from global variables")
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/178528487878.124250.14170824576025743236.stgit@devnote2
Assisted-by: Antigravity:gemini-3.5-flash
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
ac8719969e