This is what the patch does. It does not handle the case of VM resume yet. Fork safety is achieved through a generic mechanism that any userspace generator could use. The advantage the vDSO has is that it can assume that MADV_WIPEONFORK is implemented, but that's about it.

The vDSO-based approach is certainly interesting because the kernel can know exactly where randomness caches are located and zap them as needed (on fork, periodically, after VM resume). But if entire pages of memory are dedicated to buffers anyway, MADV_WIPEONFORK is sufficient for now.