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Message-ID: <alpine.LRH.2.20.1702150016220.32759@namei.org>
Date: Wed, 15 Feb 2017 00:17:24 +1100 (AEDT)
From: James Morris <jmorris@...ei.org>
To: linux-security-module@...r.kernel.org
cc: selinux@...ho.nsa.gov, kernel-hardening@...ts.openwall.com
Subject: [RFC v2 PATCH 1/2] security: introduce
CONFIG_SECURITY_WRITABLE_HOOKS
Subsequent patches will add RO hardening to LSM hooks, however, SELinux
still needs to be able to perform runtime disablement after init to handle
architectures where init-time disablement via boot parameters is not feasible.
Introduce a new kernel configuration parameter CONFIG_SECURITY_WRITABLE_HOOKS,
and a helper macro __lsm_ro_after_init, to handle this case.
Signed-off-by: James Morris <james.l.morris@...cle.com>
---
include/linux/lsm_hooks.h | 7 +++++++
security/Kconfig | 5 +++++
security/selinux/Kconfig | 6 ++++++
3 files changed, 18 insertions(+), 0 deletions(-)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index e29d4c6..c4b149f 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1908,6 +1908,13 @@ static inline void security_delete_hooks(struct security_hook_list *hooks,
}
#endif /* CONFIG_SECURITY_SELINUX_DISABLE */
+/* Currently required to handle SELinux runtime hook disable. */
+#ifdef CONFIG_SECURITY_WRITABLE_HOOKS
+#define __lsm_ro_after_init
+#else
+#define __lsm_ro_after_init __ro_after_init
+#endif /* CONFIG_SECURITY_WRITABLE_HOOKS */
+
extern int __init security_module_enable(const char *module);
extern void __init capability_add_hooks(void);
#ifdef CONFIG_SECURITY_YAMA
diff --git a/security/Kconfig b/security/Kconfig
index 118f454..f6f90c4 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -31,6 +31,11 @@ config SECURITY
If you are unsure how to answer this question, answer N.
+config SECURITY_WRITABLE_HOOKS
+ depends on SECURITY
+ bool
+ default n
+
config SECURITYFS
bool "Enable the securityfs filesystem"
help
diff --git a/security/selinux/Kconfig b/security/selinux/Kconfig
index ea7e3ef..8af7a69 100644
--- a/security/selinux/Kconfig
+++ b/security/selinux/Kconfig
@@ -40,6 +40,7 @@ config SECURITY_SELINUX_BOOTPARAM_VALUE
config SECURITY_SELINUX_DISABLE
bool "NSA SELinux runtime disable"
depends on SECURITY_SELINUX
+ select SECURITY_WRITABLE_HOOKS
default n
help
This option enables writing to a selinuxfs node 'disable', which
@@ -50,6 +51,11 @@ config SECURITY_SELINUX_DISABLE
portability across platforms where boot parameters are difficult
to employ.
+ NOTE: selecting this option will disable the '__ro_after_init'
+ kernel hardening feature for security hooks. Please consider
+ using the selinux=0 boot parameter instead of enabling this
+ option.
+
If you are unsure how to answer this question, answer N.
config SECURITY_SELINUX_DEVELOP
--
1.7.1
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