[release-1.22] Fix goroutine/memory leak in SubjectAndFiltersPass (#9152)

Fix goroutine/memory leak in SubjectAndFiltersPass

SubjectAndFiltersPass created filter objects via
CreateSubscriptionsAPIFilters on every request but never called
Cleanup() on them. The anyFilter and allFilter types each spawn a
background goroutine (optimizeLoop) that only terminates when
Cleanup() is called, causing goroutines, channels, and filter
objects to leak on every event dispatch.

Under sustained error traffic (e.g. dispatching to non-existing
sinks), this accumulated millions of leaked goroutines and
eventually caused the imc-dispatcher to OOM crash.

Co-authored-by: Christoph Stäbler <cstabler@redhat.com>

Author: knative-prow-robot

pkg/auth/event_policy.go

@@ -227,7 +227,9 @@ func SubjectAndFiltersPass(ctx context.Context, sub string, allowedSubsWithFilte
 	for _, swf := range allowedSubsWithFilters {
 		for _, s := range swf.Subjects {
 			if strings.EqualFold(s, sub) || (strings.HasSuffix(s, "*") && strings.HasPrefix(sub, strings.TrimSuffix(s, "*"))) {
-				return subscriptionsapi.CreateSubscriptionsAPIFilters(logger.Desugar(), swf.Filters).Filter(ctx, *event) != eventfilter.FailFilter
+				filter := subscriptionsapi.CreateSubscriptionsAPIFilters(logger.Desugar(), swf.Filters)
+				defer filter.Cleanup()
+				return filter.Filter(ctx, *event) != eventfilter.FailFilter
 			}
 		}
 	}