linux-kernel - [PATCH v8 0/3] mm: LSM: ro protection for dynamic data

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Message-ID: <20170627173323.11287-1-igor.stoppa@huawei.com>
Date:   Tue, 27 Jun 2017 20:33:20 +0300
From:   Igor Stoppa <igor.stoppa@...wei.com>
To:     <keescook@...omium.org>, <mhocko@...nel.org>, <jmorris@...ei.org>
CC:     <penguin-kernel@...ove.SAKURA.ne.jp>, <paul@...l-moore.com>,
        <sds@...ho.nsa.gov>, <casey@...aufler-ca.com>, <hch@...radead.org>,
        <labbott@...hat.com>, <linux-security-module@...r.kernel.org>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <kernel-hardening@...ts.openwall.com>,
        Igor Stoppa <igor.stoppa@...wei.com>
Subject: [PATCH v8 0/3] mm: LSM: ro protection for dynamic data

Hi,
please consider this patch-set for inclusion.

This patch-set introduces the possibility of protecting memory that has
been allocated dynamically.

The memory is managed in pools: when a pool is made R/O, all the memory
that is part of it, will become R/O.

A R/O pool can be destroyed, to recover its memory, but it cannot be
turned back into R/W mode.

This is intentional. This feature is meant for data that doesn't need
further modifications after initialization.

An example is provided, showing how to turn into a boot-time option the
writable state of the security hooks.
Prior to this patch, it was a compile-time option.

This is made possible, thanks to Tetsuo Handa's rework of the hooks
structure (included in the patchset).

Changes since the v6 version:
- complete rewrite, using the genalloc lib (suggested by Laura Abbott)
- added sysfs interface for tracking of active pools

Changes since the v7 version:
- replaced the use of devices with kobjects for showing info on sysfs

The only question still open is if there should be a possibility for
unprotecting a memory pool in other cases than destruction.

The only cases found for this topic are:
- protecting the LSM header structure between creation and insertion of a
  security module that was not built as part of the kernel
  (but the module can protect the headers after it has loaded)

- unloading SELinux from RedHat, if the system has booted, but no policy
  has been loaded yet - this feature is going away, according to Casey.

Note:

The patch is larg-ish, but I was not sure what criteria to use for
splitting it.
If it helps the reviewing, please do let me know how I should split it
and I will comply.

Igor Stoppa (2):
  Protectable memory support
  Make LSM Writable Hooks a command line option

Tetsuo Handa (1):
  LSM: Convert security_hook_heads into explicit array of struct
    list_head

 arch/Kconfig                   |   1 +
 include/linux/lsm_hooks.h      | 420 ++++++++++++++++++++---------------------
 include/linux/page-flags.h     |   2 +
 include/linux/pmalloc.h        | 111 +++++++++++
 include/trace/events/mmflags.h |   1 +
 init/main.c                    |   2 +
 lib/Kconfig                    |   1 +
 lib/genalloc.c                 |   4 +-
 mm/Makefile                    |   1 +
 mm/pmalloc.c                   | 341 +++++++++++++++++++++++++++++++++
 mm/usercopy.c                  |  24 ++-
 security/security.c            |  49 +++--
 12 files changed, 721 insertions(+), 236 deletions(-)
 create mode 100644 include/linux/pmalloc.h
 create mode 100644 mm/pmalloc.c

-- 
2.9.3