From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756219AbXLSWAb (ORCPT ); Wed, 19 Dec 2007 17:00:31 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752891AbXLSWAW (ORCPT ); Wed, 19 Dec 2007 17:00:22 -0500 Received: from mx1.redhat.com ([66.187.233.31]:40037 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752086AbXLSWAV (ORCPT ); Wed, 19 Dec 2007 17:00:21 -0500 Subject: [PATCH] Allow Kconfig to set default mmap_min_addr protection From: Eric Paris To: linux-kernel@vger.kernel.org Cc: jmorris@namei.org, alan@redhat.com, chrisw@redhat.com, akpm@linux-foundation.org, linux-security-module@vger.kernel.org, solar@openwall.com, wtarreau@hera.kernel.org Content-Type: text/plain Date: Wed, 19 Dec 2007 16:59:05 -0500 Message-Id: <1198101545.6197.52.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.12.2 (2.12.2-2.fc8) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Since it was decided that low memory protection from userspace couldn't be turned on by default add a Kconfig option to allow users/distros to set a default at compile time. This value is still tunable after boot in /proc/sys/vm/mmap_min_addr Signed-off-by: Eric Paris --- security/Kconfig | 18 ++++++++++++++++++ security/security.c | 4 +++- 2 files changed, 21 insertions(+), 1 deletions(-) diff --git a/security/Kconfig b/security/Kconfig index 8086e61..10c9e40 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -103,6 +103,24 @@ config SECURITY_ROOTPLUG If you are unsure how to answer this question, answer N. +config SECURITY_DEFAULT_MMAP_MIN_ADDR + int "Low address space to protect from user allocation" + depends on SECURITY + default 0 + help + This is the portion of low virtual memory which should be protected + from userspace allocation. Keeping a user from writing to low pages + can help reduce the impact of kernel NULL pointer bugs. + + For most users with lots of address space a value of 65536 is + reasonable and should cause no problems. Programs which use vm86 + functionality would either need additional permissions from either + the LSM or the capabilities module or have this protection disabled. + + This value can be changed after boot using the + /proc/sys/vm/mmap_min_addr tunable. + + source security/selinux/Kconfig endmenu diff --git a/security/security.c b/security/security.c index 0e1f1f1..c784726 100644 --- a/security/security.c +++ b/security/security.c @@ -23,7 +23,9 @@ extern struct security_operations dummy_security_ops; extern void security_fixup_ops(struct security_operations *ops); struct security_operations *security_ops; /* Initialized to NULL */ -unsigned long mmap_min_addr; /* 0 means no protection */ + +/* amount of vm to protect from userspace access */ +unsigned long mmap_min_addr = CONFIG_SECURITY_DEFAULT_MMAP_MIN_ADDR; static inline int verify(struct security_operations *ops) {