On Fri, Jun 12, 2020 at 11:38:33AM -0700, Kees Cook wrote: > On Fri, Jun 12, 2020 at 08:28:16PM +0200, Christian Brauner wrote: > > Al didn't want the PAGE_SIZE limit in there because there's nothing > > inherently wrong with copying insane amounts of memory. > > Right, ok. > > > (Another tangent. I've asked this on Twitter not too long ago: do we > > have stats how long copy_from_user()/copy_struct_from_user() takes with > > growing struct/memory size? I'd be really interested in this. I have a > > feeling that clone3()'s and - having had a chat with David Howells - > > openat2()'s structs will continue to grow for a while... and I'd really > > like to have some numbers on when copy_struct_from_user() becomes > > costly or how costly it becomes.) > > How long it takes? It should be basically the same, the costs should be > mostly in switching memory protections, etc. I wouldn't imagine how many > bytes being copied would matter much here, given the sub-page sizes. This makes me _very_ happy. Christian
