On Wed, Nov 04, 2020 at 05:26:58PM +0100, Daniel Vetter wrote: > What we're discussing is whether gup_fast and pup_fast also obey this, > or fall over and can give you the struct page that's backing the > dma_mmap_* memory. Since the _fast variant doesn't check for > vma->vm_flags, and afaict that's the only thing which closes this gap. > And like you restate, that would be a bit a problem. So where's that > check which Jason&me aren't spotting? remap_pte_range uses pte_mkspecial to set up the PTEs, and gup_pte_range errors out on pte_special. Of course this only works for the CONFIG_ARCH_HAS_PTE_SPECIAL case, for other architectures we do have a real problem.
