Re: [RFC][PATCH 0/3] Sanitization of buddy pages

From: Laura Abbott
Date: Tue Jan 26 2016 - 15:34:30 EST

On 01/25/2016 10:05 PM, Sasha Levin wrote:
On 01/25/2016 11:55 AM, Laura Abbott wrote:

This is an implementation of page poisoning/sanitization for all arches. It
takes advantage of the existing implementation for
!ARCH_SUPPORTS_DEBUG_PAGEALLOC arches. This is a different approach than what
the Grsecurity patches were taking but should provide equivalent functionality.

For those who aren't familiar with this, the goal of sanitization is to reduce
the severity of use after free and uninitialized data bugs. Memory is cleared
on free so any sensitive data is no longer available. Discussion of
sanitization was brough up in a thread about CVEs

I eventually expect Kconfig names will want to be changed and or moved if this
is going to be used for security but that can happen later.

Credit to Mathias Krause for the version in grsecurity

Laura Abbott (3):
mm/debug-pagealloc.c: Split out page poisoning from debug page_alloc
mm/page_poison.c: Enable PAGE_POISONING as a separate option
mm/page_poisoning.c: Allow for zero poisoning

Documentation/kernel-parameters.txt | 5 ++
include/linux/mm.h | 13 +++
include/linux/poison.h | 4 +
mm/Kconfig.debug | 35 +++++++-
mm/Makefile | 5 +-
mm/debug-pagealloc.c | 127 +----------------------------
mm/page_alloc.c | 10 ++-
mm/page_poison.c | 158 ++++++++++++++++++++++++++++++++++++
8 files changed, 228 insertions(+), 129 deletions(-)
create mode 100644 mm/page_poison.c

Should poisoning of this kind be using kasan rather than "old fashioned"

The two aren't mutually exclusive. kasan is serving a different purpose even
though it has sanitize in the name. kasan is designed to detect errors, the
purpose of this series is to make sure the memory is really cleared out.
This series also doesn't have the memory overhead of kasan.