]> git.proxmox.com Git - mirror_ubuntu-kernels.git/commit
mm: add SLUB free list pointer obfuscation
authorKees Cook <keescook@chromium.org>
Wed, 6 Sep 2017 23:19:18 +0000 (16:19 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Thu, 7 Sep 2017 00:27:24 +0000 (17:27 -0700)
commit2482ddec670fb83717d129012bc558777cb159f7
tree5c6b4c474757e143f6bc3d3f4220371e9dd5123d
parentea37df54d2b7950d607800ee417a1d59b95068c2
mm: add SLUB free list pointer obfuscation

This SLUB free list pointer obfuscation code is modified from Brad
Spengler/PaX Team's code in the last public patch of grsecurity/PaX
based on my understanding of the code.  Changes or omissions from the
original code are mine and don't reflect the original grsecurity/PaX
code.

This adds a per-cache random value to SLUB caches that is XORed with
their freelist pointer address and value.  This adds nearly zero
overhead and frustrates the very common heap overflow exploitation
method of overwriting freelist pointers.

A recent example of the attack is written up here:

  http://cyseclabs.com/blog/cve-2016-6187-heap-off-by-one-exploit

and there is a section dedicated to the technique the book "A Guide to
Kernel Exploitation: Attacking the Core".

This is based on patches by Daniel Micay, and refactored to minimize the
use of #ifdef.

With 200-count cycles of "hackbench -g 20 -l 1000" I saw the following
run times:

 before:
  mean 10.11882499999999999995
variance .03320378329145728642
stdev .18221905304181911048

  after:
mean 10.12654000000000000014
variance .04700556623115577889
stdev .21680767106160192064

The difference gets lost in the noise, but if the above is to be taken
literally, using CONFIG_FREELIST_HARDENED is 0.07% slower.

Link: http://lkml.kernel.org/r/20170802180609.GA66807@beast
Signed-off-by: Kees Cook <keescook@chromium.org>
Suggested-by: Daniel Micay <danielmicay@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Tycho Andersen <tycho@docker.com>
Cc: Alexander Popov <alex.popov@linux.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
include/linux/slub_def.h
init/Kconfig
mm/slub.c