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perf/ftrace: Fix WARNING in __unregister_ftrace_function

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perf_ftrace_function_unregister() unconditionally calls
unregister_ftrace_function() without checking whether the ftrace_ops
was ever successfully registered. This triggers a WARN_ON in
__unregister_ftrace_function() when the ops doesn't have
FTRACE_OPS_FL_ENABLED set.

This can happen during perf_event_alloc() error cleanup when
perf_trace_destroy() is called via __free_event() on an event whose
ftrace_ops registration failed or was already torn down by
perf_try_init_event()'s err_destroy path.

The call path is:
  perf_event_alloc() error cleanup
    -> __free_event()
      -> event->destroy() [tp_perf_event_destroy]
        -> perf_trace_destroy()
          -> perf_trace_event_close()
            -> TRACE_REG_PERF_CLOSE
              -> perf_ftrace_function_unregister()
                -> unregister_ftrace_function()
                  -> __unregister_ftrace_function()
                    -> WARN_ON(!(ops->flags & FTRACE_OPS_FL_ENABLED))

Fix this by checking FTRACE_OPS_FL_ENABLED before attempting to
unregister. If the ops is not enabled, just free the filter and
return success.

Link: https://patch.msgid.link/20260527111301.2d0d8256@fangorn
Signed-off-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Rik van Riel 2026-05-27 11:13:01 -04:00 committed by Steven Rostedt
parent 0104607288
commit 9581123304
1 changed files with 11 additions and 1 deletions
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12
kernel/trace/trace_event_perf.c
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@ -497,7 +497,17 @@ static int perf_ftrace_function_register(struct perf_event *event)
static int perf_ftrace_function_unregister(struct perf_event *event)
{
struct ftrace_ops *ops = &event->ftrace_ops;
int ret = unregister_ftrace_function(ops);
int ret = 0;
/*
* Perf will call this unconditionally even if the ops is not
* enabled. The unregister_ftrace_function() will warn if called
* when not enabled. Just bypass the unregistering if ops isn't
* enabled here.
*/
if (ops->flags & FTRACE_OPS_FL_ENABLED)
ret = unregister_ftrace_function(ops);
ftrace_free_filter(ops);
return ret;
}