diff options
| author | Kees Cook <keescook@chromium.org> | 2017-09-06 16:19:18 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-09-06 17:27:24 -0700 |
| commit | 2482ddec670fb83717d129012bc558777cb159f7 (patch) | |
| tree | 5c6b4c474757e143f6bc3d3f4220371e9dd5123d /include | |
| parent | ea37df54d2b7950d607800ee417a1d59b95068c2 (diff) | |
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>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/slub_def.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h index cc0faf3a90be..0783b622311e 100644 --- a/include/linux/slub_def.h +++ b/include/linux/slub_def.h @@ -115,6 +115,10 @@ struct kmem_cache { #endif #endif +#ifdef CONFIG_SLAB_FREELIST_HARDENED + unsigned long random; +#endif + #ifdef CONFIG_NUMA /* * Defragmentation by allocating from a remote node. |