Contributed by tbert on 2014-05-14 from the four-card-monte dept.

Recently, Ted Unangst (tedu@) committed a tweak for malloc(3) freelists:

CVSROOT: /cvs Module name: src Changes by: tedu@cvs.openbsd.org 2014/05/12 13:02:20 Modified files: lib/libc/stdlib: malloc.c Log message: change to having four freelists per size, to reduce another source of deterministic behavior. four selected because it's more than three, less than five. i.e., no particular reason.

and astute readers will recall a similarly-themed change for kernel pool(9) freelists.

These changes make it much harder for bugs which require the immediate recycling of freed memory, an example of which was famously unearthed during the heartbleed fallout, to go undiscovered.