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Date: Wed, 9 Mar 2016 13:00:48 -0800
From: Kees Cook <keescook@...omium.org>
To: Laura Abbott <labbott@...oraproject.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Vlastimil Babka <vbabka@...e.cz>,
Michal Hocko <mhocko@...e.com>, Linux-MM <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCHv4 0/2] Sanitization of buddy pages
On Fri, Mar 4, 2016 at 3:50 PM, Laura Abbott <labbott@...oraproject.org> wrote:
> Hi,
>
> This is v4 of the santization of buddy pages. This is mostly just a rebase
> and some phrasing tweaks from v2. Kees submitted a rebase of v3 so this is v4.
>
> Kees, I'm hoping you will give your Tested-by and provide some stats from the
> tests you were running before.
Yeah, please consider these:
Tested-by: Kees Cook <keescook@...omium.org>
The benchmarking should be the same as the v3 I reported on, repeated
here for good measure:
The sanity checks appear to add about 3% additional overhead, but
poisoning seems to add about 9%.
DEBUG_PAGEALLOC=n
PAGE_POISONING=y
PAGE_POISONING_NO_SANITY=y
PAGE_POISONING_ZERO=y
Run times: 389.23 384.88 386.33
Mean: 386.81
Std Dev: 1.81
LKDTM detects nothing, as expected.
DEBUG_PAGEALLOC=n
PAGE_POISONING=y
PAGE_POISONING_NO_SANITY=y
PAGE_POISONING_ZERO=n
slub_debug=P page_poison=on
Run times: 435.63 419.20 422.82
Mean: 425.89
Std Dev: 7.05
Overhead: 9.2% vs all disabled
Poisoning confirmed: READ_AFTER_FREE, READ_BUDDY_AFTER_FREE
Writes not detected, as expected.
DEBUG_PAGEALLOC=n
PAGE_POISONING=y
PAGE_POISONING_NO_SANITY=y
PAGE_POISONING_ZERO=y
slub_debug=P page_poison=on
Run times: 423.44 422.32 424.95
Mean: 423.57
Std Dev: 1.08
Overhead 8.7% overhead vs disabled, 0.5% improvement over non-zero
poison (though only the buddy allocator is using the zero poison).
Poisoning confirmed: READ_AFTER_FREE, READ_BUDDY_AFTER_FREE
Writes not detected, as expected.
DEBUG_PAGEALLOC=n
PAGE_POISONING=y
PAGE_POISONING_NO_SANITY=n
PAGE_POISONING_ZERO=y
slub_debug=FP page_poison=on
Run times: 454.26 429.46 430.48
Mean: 438.07
Std Dev: 11.46
Overhead: 11.7% vs nothing, 3% more overhead than no sanitizing.
All four tests detect correctly.
>
> Thanks,
> Laura
>
> Laura Abbott (2):
> 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 | 11 +++
> include/linux/poison.h | 4 +
> kernel/power/hibernate.c | 17 ++++
> mm/Kconfig.debug | 39 +++++++-
> mm/Makefile | 2 +-
> mm/debug-pagealloc.c | 137 ----------------------------
> mm/page_alloc.c | 13 ++-
> mm/page_ext.c | 10 +-
> mm/page_poison.c | 176 ++++++++++++++++++++++++++++++++++++
> 10 files changed, 272 insertions(+), 142 deletions(-)
> delete mode 100644 mm/debug-pagealloc.c
> create mode 100644 mm/page_poison.c
>
> --
> 2.5.0
>
-Kees
--
Kees Cook
Chrome OS & Brillo Security
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