On Tue, Mar 27, 2018 at 4:49 PM, Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > On Tue, Mar 27, 2018 at 03:53:53PM -0700, Kees Cook wrote: >> I agree: pushing this off to libc leaves a lot of things unprotected. >> I think this should live in the kernel. The question I have is about >> making it maintainable/readable/etc. >> >> The state-of-the-art for ASLR is moving to finer granularity (over >> just base-address offset), so I'd really like to see this supported in >> the kernel. We'll be getting there for other things in the future, and >> I'd like to have a working production example for researchers to >> study, etc. > > One thing we need is to limit the fragmentation of this approach. > Even on 64-bit systems, we can easily get into a situation where there isn't > space to map a contiguous terabyte. FWIW, I wouldn't expect normal systems to use this. I am curious about fragmentation vs entropy though. Are workloads with a mis of lots of tiny allocations and TB-allocations? AIUI, glibc uses larger mmap() regions for handling tiny mallocs(). -Kees -- Kees Cook Pixel Security
