LSM: Plumb visibility into optional "enabled" state

In preparation for lifting the "is this LSM enabled?" logic out of the
individual LSMs, pass in any special enabled state tracking (as needed
for SELinux, AppArmor, and LoadPin). This should be an "int" to include
handling any future cases where "enabled" is exposed via sysctl which
has no "bool" type.

Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: John Johansen <john.johansen@canonical.com>

include/linux/lsm_hooks.h

@@ -2047,6 +2047,7 @@ extern void security_add_hooks(struct security_hook_list *hooks, int count,
 struct lsm_info {
 	const char *name;	/* Required. */
 	unsigned long flags;	/* Optional: flags describing LSM */
+	int *enabled;		/* Optional: NULL means enabled. */
 	int (*init)(void);	/* Required. */
 };
 

security/apparmor/lsm.c

@@ -1333,8 +1333,8 @@ bool aa_g_paranoid_load = true;
 module_param_named(paranoid_load, aa_g_paranoid_load, aabool, S_IRUGO);
 
 /* Boot time disable flag */
-static bool apparmor_enabled = CONFIG_SECURITY_APPARMOR_BOOTPARAM_VALUE;
-module_param_named(enabled, apparmor_enabled, bool, S_IRUGO);
+static int apparmor_enabled = CONFIG_SECURITY_APPARMOR_BOOTPARAM_VALUE;
+module_param_named(enabled, apparmor_enabled, int, 0444);
 
 static int __init apparmor_enabled_setup(char *str)
 {
@@ -1730,5 +1730,6 @@ alloc_out:
 DEFINE_LSM(apparmor) = {
 	.name = "apparmor",
 	.flags = LSM_FLAG_LEGACY_MAJOR,
+	.enabled = &apparmor_enabled,
 	.init = apparmor_init,
 };

security/selinux/hooks.c

@@ -7000,6 +7000,7 @@ void selinux_complete_init(void)
 DEFINE_LSM(selinux) = {
 	.name = "selinux",
 	.flags = LSM_FLAG_LEGACY_MAJOR,
+	.enabled = &selinux_enabled,
 	.init = selinux_init,
 };