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[v7,0/3] add init_on_alloc/init_on_free boot options

Message ID 20190617151050.92663-1-glider@google.com (mailing list archive)
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Series add init_on_alloc/init_on_free boot options | expand

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Alexander Potapenko June 17, 2019, 3:10 p.m. UTC 
Provide init_on_alloc and init_on_free boot options.

These are aimed at preventing possible information leaks and making the
control-flow bugs that depend on uninitialized values more deterministic.

Enabling either of the options guarantees that the memory returned by the
page allocator and SL[AU]B is initialized with zeroes.
SLOB allocator isn't supported at the moment, as its emulation of kmem
caches complicates handling of SLAB_TYPESAFE_BY_RCU caches correctly.

Enabling init_on_free also guarantees that pages and heap objects are
initialized right after they're freed, so it won't be possible to access
stale data by using a dangling pointer.

As suggested by Michal Hocko, right now we don't let the heap users to
disable initialization for certain allocations. There's not enough
evidence that doing so can speed up real-life cases, and introducing
ways to opt-out may result in things going out of control.

To: Andrew Morton <akpm@linux-foundation.org>
To: Christoph Lameter <cl@linux.com>
To: Kees Cook <keescook@chromium.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: James Morris <jmorris@namei.org>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Kostya Serebryany <kcc@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Sandeep Patil <sspatil@android.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Jann Horn <jannh@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Marco Elver <elver@google.com>
Cc: linux-mm@kvack.org
Cc: linux-security-module@vger.kernel.org
Cc: kernel-hardening@lists.openwall.com

Alexander Potapenko (2):
  mm: security: introduce init_on_alloc=1 and init_on_free=1 boot
    options
  mm: init: report memory auto-initialization features at boot time

 .../admin-guide/kernel-parameters.txt         |  9 +++
 drivers/infiniband/core/uverbs_ioctl.c        |  2 +-
 include/linux/mm.h                            | 22 +++++++
 init/main.c                                   | 24 +++++++
 kernel/kexec_core.c                           |  2 +-
 mm/dmapool.c                                  |  2 +-
 mm/page_alloc.c                               | 63 ++++++++++++++++---
 mm/slab.c                                     | 16 ++++-
 mm/slab.h                                     | 19 ++++++
 mm/slub.c                                     | 33 ++++++++--
 net/core/sock.c                               |  2 +-
 security/Kconfig.hardening                    | 29 +++++++++
 12 files changed, 204 insertions(+), 19 deletions(-)
---
 v3: dropped __GFP_NO_AUTOINIT patches
 v5: dropped support for SLOB allocator, handle SLAB_TYPESAFE_BY_RCU
 v6: changed wording in boot-time message
 v7: dropped the test_meminit.c patch (picked by Andrew Morton already),
     minor wording changes