Date:	Tue, 21 Jul 2015 12:09:46 -0700
From:	Kees Cook <keescook@...omium.org>
To:	linux-security-module@...r.kernel.org
Cc:	Casey Schaufler <casey@...aufler-ca.com>,
	James Morris <james.l.morris@...cle.com>,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] Yama: remove needless CONFIG_SECURITY_YAMA_STACKED

Now that minor LSMs can cleanly stack with major LSMs, remove the unneeded
config for Yama to be made to explicitly stack. Just selecting the main
Yama CONFIG will allow it to work, regardless of the major LSM. Since
distros using Yama are already forcing it to stack, this is effectively
a no-op change.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 Documentation/security/Yama.txt       | 10 ++++------
 arch/mips/configs/pistachio_defconfig |  1 -
 include/linux/lsm_hooks.h             |  3 ---
 security/security.c                   | 11 ++---------
 security/yama/Kconfig                 |  9 +--------
 security/yama/yama_lsm.c              | 26 +++++++++-----------------
 6 files changed, 16 insertions(+), 44 deletions(-)

diff --git a/Documentation/security/Yama.txt b/Documentation/security/Yama.txt
index 227a63f018a2..d9ee7d7a6c7f 100644
--- a/Documentation/security/Yama.txt
+++ b/Documentation/security/Yama.txt
@@ -1,9 +1,7 @@
-Yama is a Linux Security Module that collects a number of system-wide DAC
-security protections that are not handled by the core kernel itself. To
-select it at boot time, specify "security=yama" (though this will disable
-any other LSM).
-
-Yama is controlled through sysctl in /proc/sys/kernel/yama:
+Yama is a Linux Security Module that collects system-wide DAC security
+protections that are not handled by the core kernel itself. This is
+selectable at build-time with CONFIG_SECURITY_YAMA, and can be controlled
+at run-time through sysctls in /proc/sys/kernel/yama:
 
 - ptrace_scope
 
diff --git a/arch/mips/configs/pistachio_defconfig b/arch/mips/configs/pistachio_defconfig
index 1646cce032c3..642b50946943 100644
--- a/arch/mips/configs/pistachio_defconfig
+++ b/arch/mips/configs/pistachio_defconfig
@@ -320,7 +320,6 @@ CONFIG_KEYS=y
 CONFIG_SECURITY=y
 CONFIG_SECURITY_NETWORK=y
 CONFIG_SECURITY_YAMA=y
-CONFIG_SECURITY_YAMA_STACKED=y
 CONFIG_DEFAULT_SECURITY_DAC=y
 CONFIG_CRYPTO_AUTHENC=y
 CONFIG_CRYPTO_HMAC=y
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 9429f054c323..4ea92e8968c8 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1881,8 +1881,5 @@ static inline void security_delete_hooks(struct security_hook_list *hooks,
 
 extern int __init security_module_enable(const char *module);
 extern void __init capability_add_hooks(void);
-#ifdef CONFIG_SECURITY_YAMA_STACKED
-void __init yama_add_hooks(void);
-#endif
 
 #endif /* ! __LINUX_LSM_HOOKS_H */
diff --git a/security/security.c b/security/security.c
index 595fffab48b0..aada79d281e5 100644
--- a/security/security.c
+++ b/security/security.c
@@ -56,18 +56,11 @@ int __init security_init(void)
 	pr_info("Security Framework initialized\n");
 
 	/*
-	 * Always load the capability module.
+	 * Always load the capability module first.
 	 */
 	capability_add_hooks();
-#ifdef CONFIG_SECURITY_YAMA_STACKED
 	/*
-	 * If Yama is configured for stacking load it next.
-	 */
-	yama_add_hooks();
-#endif
-	/*
-	 * Load the chosen module if there is one.
-	 * This will also find yama if it is stacking
+	 * Load all the remaining security modules.
 	 */
 	do_security_initcalls();
 
diff --git a/security/yama/Kconfig b/security/yama/Kconfig
index 3123e1da2fed..90c605eea892 100644
--- a/security/yama/Kconfig
+++ b/security/yama/Kconfig
@@ -6,14 +6,7 @@ config SECURITY_YAMA
 	  This selects Yama, which extends DAC support with additional
 	  system-wide security settings beyond regular Linux discretionary
 	  access controls. Currently available is ptrace scope restriction.
+	  Like capabilities, this security module stacks with other LSMs.
 	  Further information can be found in Documentation/security/Yama.txt.
 
 	  If you are unsure how to answer this question, answer N.
-
-config SECURITY_YAMA_STACKED
-	bool "Yama stacked with other LSMs"
-	depends on SECURITY_YAMA
-	default n
-	help
-	  When Yama is built into the kernel, force it to stack with the
-	  selected primary LSM.
diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
index 9ed32502470e..15ce2bac75e3 100644
--- a/security/yama/yama_lsm.c
+++ b/security/yama/yama_lsm.c
@@ -353,11 +353,6 @@ static struct security_hook_list yama_hooks[] = {
 	LSM_HOOK_INIT(task_free, yama_task_free),
 };
 
-void __init yama_add_hooks(void)
-{
-	security_add_hooks(yama_hooks, ARRAY_SIZE(yama_hooks));
-}
-
 #ifdef CONFIG_SYSCTL
 static int yama_dointvec_minmax(struct ctl_table *table, int write,
 				void __user *buffer, size_t *lenp, loff_t *ppos)
@@ -396,23 +391,20 @@ static struct ctl_table yama_sysctl_table[] = {
 	},
 	{ }
 };
+static __init void yama_init_sysctl(void)
+{
+	if (!register_sysctl_paths(yama_sysctl_path, yama_sysctl_table))
+		panic("Yama: sysctl registration failed.\n");
+}
+#else
+static __init void yama_init_sysctl(void) { };
 #endif /* CONFIG_SYSCTL */
 
 static __init int yama_init(void)
 {
-#ifndef CONFIG_SECURITY_YAMA_STACKED
-	/*
-	 * If yama is being stacked this is already taken care of.
-	 */
-	if (!security_module_enable("yama"))
-		return 0;
-#endif
 	pr_info("Yama: becoming mindful.\n");
-
-#ifdef CONFIG_SYSCTL
-	if (!register_sysctl_paths(yama_sysctl_path, yama_sysctl_table))
-		panic("Yama: sysctl registration failed.\n");
-#endif
+	security_add_hooks(yama_hooks, ARRAY_SIZE(yama_hooks));
+	yama_init_sysctl();
 
 	return 0;
 }
-- 
1.9.1


-- 
Kees Cook
Chrome OS Security
--
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