Daniel Micay wrote: > > The current OpenBSD code only wipes up to MALLOC_MAXCHUNK with junk @ 1, > and it similarly doesn't wipe at all with 'U' (even though junk-on-free > also serves the purpose of preventing information leaks, not just > mitigating use-after-free). IMO, optimizing large allocation perf like > this isn't worthwhile.
this requires some analysis of what programs do in the wild. some programs preemptively malloc large buffers, but don't touch them. it would be a serious reqression for free to fault in new pages, just to ditry them, then turn around and unmap them. some of this is because i believe the code is doing things at the wrong time. if you want to dirty whole pages, it should be when they go on the freelist, not immediately.
