promhttp instrumented handler hangs with the invalid metric name

[AlekSi]

client_golang/prometheus/promhttp/instrument_server.go

Lines 228 to 232 in 47cfdc9

	// Create a ConstMetric with the Desc. Since we don't know how many
	// variable labels there are, try for as long as it needs.
	for err := errors.New("dummy"); err != nil; lvs = append(lvs, magicString) {
	m, err = prometheus.NewConstMetric(desc, prometheus.UntypedValue, 0, lvs...)
	}

This code does not check what error is returned. If an invalid metric name is passed, the process consumes all memory and is killed by the OOM killer.

I found it when I passed sub-test's t.Name() as a part of the metric name: / can't a part of the metric name.