On Thu, May 23, 2019 at 02:24:58PM -0400, Jerome Glisse wrote: > I can not take mmap_sem in range_register, the READ_ONCE is fine and > they are no race as we do take a reference on the hmm struct thus Of course there are use after free races with a READ_ONCE scheme, I shouldn't have to explain this. If you cannot take the read mmap sem (why not?), then please use my version and push the update to the driver through -mm.. Jason