This kind of passive is formed with si + 3th person singular or plural of the verb. In this case the sentence has a general meaning (everybody, people etc.)

I have already  spoken about the passive form with the verb essere, now I’d like to explain the passive voice with the verb venire + the past paticiple. A characteristic: this kind of passive can be used only with simple tenses (like present, imperfect, historical past, future tense) and NOT with compound tenses (example: present [...]