On Tue, Jan 19, 2021 at 03:14:04PM -0500, Pavel Tatashin wrote: > I was thinking about a use case where userland would pin an address > without FOLL_WRITE, because the PTE for that address is not going to > be writable, but some device via DMA will write to it. That would be a serious bug in the get_user_pages caller to write to a page without using FOLL_WRITE Jason