linux-kernel - [PATCH 06/12] __wr_after_init: Documentation: self-protection

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Message-Id: <20181219213338.26619-7-igor.stoppa@huawei.com>
Date:   Wed, 19 Dec 2018 23:33:32 +0200
From:   Igor Stoppa <igor.stoppa@...il.com>
To:     Andy Lutomirski <luto@...capital.net>,
        Matthew Wilcox <willy@...radead.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:     igor.stoppa@...wei.com, Nadav Amit <nadav.amit@...il.com>,
        Kees Cook <keescook@...omium.org>,
        linux-integrity@...r.kernel.org,
        kernel-hardening@...ts.openwall.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 06/12] __wr_after_init: Documentation: self-protection

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

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

CC: Andy Lutomirski <luto@...capital.net>
CC: Nadav Amit <nadav.amit@...il.com>
CC: Matthew Wilcox <willy@...radead.org>
CC: Peter Zijlstra <peterz@...radead.org>
CC: Kees Cook <keescook@...omium.org>
CC: Dave Hansen <dave.hansen@...ux.intel.com>
CC: Mimi Zohar <zohar@...ux.vnet.ibm.com>
CC: linux-integrity@...r.kernel.org
CC: kernel-hardening@...ts.openwall.com
CC: linux-mm@...ck.org
CC: linux-kernel@...r.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