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Message-ID: <ff1f408b-cf37-7df0-2393-7bc2078f6c63@infradead.org>
Date: Thu, 18 Apr 2019 15:08:37 -0700
From: Randy Dunlap <rdunlap@...radead.org>
To: Alexander Potapenko <glider@...gle.com>, akpm@...ux-foundation.org,
cl@...ux.com, dvyukov@...gle.com, keescook@...omium.org, labbott@...hat.com
Cc: linux-mm@...ck.org, linux-security-module@...r.kernel.org,
kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH 1/3] mm: security: introduce the init_allocations=1 boot
option
On 4/18/19 8:42 AM, Alexander Potapenko wrote:
> This option adds the possibility to initialize newly allocated pages and
> heap objects with zeroes. This is needed to prevent possible information
> leaks and make the control-flow bugs that depend on uninitialized values
> more deterministic.
>
> Initialization is done at allocation time at the places where checks for
> __GFP_ZERO are performed. We don't initialize slab caches with
> constructors to preserve their semantics. To reduce runtime costs of
> checking cachep->ctor we replace a call to memset with a call to
> cachep->poison_fn, which is only executed if the memory block needs to
> be initialized.
>
> For kernel testing purposes filling allocations with a nonzero pattern
> would be more suitable, but may require platform-specific code. To have
> a simple baseline we've decided to start with zero-initialization.
>
> No performance optimizations are done at the moment to reduce double
> initialization of memory regions.
>
> Signed-off-by: Alexander Potapenko <glider@...gle.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: James Morris <jmorris@...ei.org>
> Cc: "Serge E. Hallyn" <serge@...lyn.com>
> Cc: Nick Desaulniers <ndesaulniers@...gle.com>
> Cc: Kostya Serebryany <kcc@...gle.com>
> Cc: Dmitry Vyukov <dvyukov@...gle.com>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Sandeep Patil <sspatil@...roid.com>
> Cc: Laura Abbott <labbott@...hat.com>
> Cc: Randy Dunlap <rdunlap@...radead.org>
> Cc: Jann Horn <jannh@...gle.com>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Qian Cai <cai@....pw>
> Cc: Vlastimil Babka <vbabka@...e.cz>
> Cc: linux-mm@...ck.org
> Cc: linux-security-module@...r.kernel.org
> Cc: kernel-hardening@...ts.openwall.com
> ---
> drivers/infiniband/core/uverbs_ioctl.c | 2 +-
> include/linux/mm.h | 8 ++++++++
> include/linux/slab_def.h | 1 +
> include/linux/slub_def.h | 1 +
> kernel/kexec_core.c | 2 +-
> mm/dmapool.c | 2 +-
> mm/page_alloc.c | 18 +++++++++++++++++-
> mm/slab.c | 12 ++++++------
> mm/slab.h | 1 +
> mm/slab_common.c | 15 +++++++++++++++
> mm/slob.c | 2 +-
> mm/slub.c | 8 ++++----
> net/core/sock.c | 2 +-
> 13 files changed, 58 insertions(+), 16 deletions(-)
>
Hi,
Please document init_allocations=N in Documentation/admin-guide/kernel-parameters.txt.
thanks.
--
~Randy
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