Linux distributions that have not patched their long-term kernels with
https://git.kernel.org/linus/a87938b2e246b81b4fb713edb371a9fa3c5c3c86
(committed on April 14, 2015). This kernel vulnerability was fixed in April
2015 by commit a87938b2e246b81b4fb713edb371a9fa3c5c3c86 (backported to
Linux 3.10.77 in May 2015), but it was not recognized as a security threat.
With CONFIG_ARCH_BINFMT_ELF_RANDOMIZE_PIE enabled, and a normal top-down
address allocation strategy, load_elf_binary() will attempt to map a PIE
binary into an address range immediately below mm->mmap_base.
Unfortunately, load_elf_ binary() does not take account of the need to
allocate sufficient space for the entire binary which means that, while the
first PT_LOAD segment is mapped below mm->mmap_base, the subsequent PT_LOAD
segment(s) end up being mapped above mm->mmap_base into the are that is
supposed to be the "gap" between the stack and the binary.