On Mon, Dec 21, 2020 at 12:26:22PM -0800, Linus Torvalds wrote: > On Mon, Dec 21, 2020 at 12:23 PM Nadav Amit <nadav.amit@xxxxxxxxx> wrote: > > > > Using mmap_write_lock() was my initial fix and there was a strong pushback > > on this approach due to its potential impact on performance. > > From whom? > > Somebody who doesn't understand that correctness is more important > than performance? And that userfaultfd is not the most important part > of the system? > > The fact is, userfaultfd is CLEARLY BUGGY. > > Linus Fair enough. Nadav, for your patch (you might want to update the commit message). Reviewed-by: Yu Zhao <yuzhao@xxxxxxxxxx> While we are all here, there is also clear_soft_dirty() that could use a similar fix...