Ms.Vivian, in principal, you need a visa to China if you fly to Shanghai directly from Canada because the Home Return Card is issued to HKSAR Residents, a China visa is not required if the holders go to China from Hong Kong.

However, in most situations, the Home Return Card holders go to China directly from foreign countries without a China visa, except for strict border check, you won't face problems by holding the Home Return Card to go to China without a China visa.