[RFC PATCH v5 07/12] __wr_after_init: Documentation: self-protection

From: Igor Stoppa <igor.stoppa@gmail.com>
To: unlisted-recipients:; (no To-header on input)
Cc: Igor Stoppa <igor.stoppa@huawei.com>,
	Andy Lutomirski <luto@amacapital.net>,
	Nadav Amit <nadav.amit@gmail.com>,
	Matthew Wilcox <willy@infradead.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Kees Cook <keescook@chromium.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Mimi Zohar <zohar@linux.vnet.ibm.com>,
	Thiago Jung Bauermann <bauerman@linux.ibm.com>,
	Ahmed Soliman <ahmedsoliman@mena.vt.edu>,
	linux-integrity@vger.kernel.org,
	kernel-hardening@lists.openwall.com, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: [RFC PATCH v5 07/12] __wr_after_init: Documentation: self-protection
Date: Thu, 14 Feb 2019 00:41:36 +0200	[thread overview]
Message-ID: <f0335476914a519f573d271ef062dc02b39885d1.1550097697.git.igor.stoppa@huawei.com> (raw)
In-Reply-To: <cover.1550097697.git.igor.stoppa@huawei.com>

Update the self-protection documentation, to mention also the use of the
__wr_after_init attribute.

Signed-off-by: Igor Stoppa <igor.stoppa@huawei.com>

CC: Andy Lutomirski <luto@amacapital.net>
CC: Nadav Amit <nadav.amit@gmail.com>
CC: Matthew Wilcox <willy@infradead.org>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Kees Cook <keescook@chromium.org>
CC: Dave Hansen <dave.hansen@linux.intel.com>
CC: Mimi Zohar <zohar@linux.vnet.ibm.com>
CC: Thiago Jung Bauermann <bauerman@linux.ibm.com>
CC: Ahmed Soliman <ahmedsoliman@mena.vt.edu>
CC: linux-integrity@vger.kernel.org
CC: kernel-hardening@lists.openwall.com
CC: linux-mm@kvack.org
CC: linux-kernel@vger.kernel.org
---
 Documentation/security/self-protection.rst | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/Documentation/security/self-protection.rst b/Documentation/security/self-protection.rst
index f584fb74b4ff..df2614bc25b9 100644
--- a/Documentation/security/self-protection.rst
+++ b/Documentation/security/self-protection.rst
@@ -84,12 +84,14 @@ For variables that are initialized once at ``__init`` time, these can
 be marked with the (new and under development) ``__ro_after_init``
 attribute.
 
-What remains are variables that are updated rarely (e.g. GDT). These
-will need another infrastructure (similar to the temporary exceptions
-made to kernel code mentioned above) that allow them to spend the rest
-of their lifetime read-only. (For example, when being updated, only the
-CPU thread performing the update would be given uninterruptible write
-access to the memory.)
+Others, which are statically allocated, but still need to be updated
+rarely, can be marked with the ``__wr_after_init`` attribute.
+
+The update mechanism must avoid exposing the data to rogue alterations
+during the update. For example, only the CPU thread performing the update
+would be given uninterruptible write access to the memory.
+
+Currently there is no protection available for data allocated dynamically.
 
 Segregation of kernel memory from userspace memory
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- 
2.19.1

