成唯識論述記 6.285

6.285

述曰：「苦」謂三苦，「苦具」即彼能生苦者，一切皆是。准無貪中。滅諦、涅槃亦是苦具，違理生故。

The Commentary states: "Suffering" refers to the three kinds of suffering; "requisites of suffering" refers to everything that can produce that suffering. By analogy with non-greed, the truth of cessation and nirvāṇa are also requisites of suffering, because [hostility toward them] arises contrary to principle.