If I had to guess, I would say that this is probably going to be another R. coriifolia var. froebelii, the Caninae rootstock that is commonly called "Rosa laxa" in Europe, but is not R. laxa Retz. The unfortunate synonym has led to the same confusion again and again, and the fact that both have grayish leaves with white flowers doesn't help matters.

That looks a lot like R. corymbifera 'laxa'.