LoadPin: Rename boot param "enabled" to "enforce"

kees · kees · commit 13523bef1e21 · 2018-10-18T15:29:44.000-07:00
LoadPin's "enabled" setting is really about enforcement, not whether
or not the LSM is using LSM hooks. Instead, split this out so that LSM
enabling can be logically distinct from whether enforcement is happening
(for example, the pinning happens when the LSM is enabled, but the pin
is only checked when "enforce" is set). This allows LoadPin to continue
to operate sanely in test environments once LSM enable/disable is
centrally handled (i.e. we want LoadPin to be enabled separately from
its enforcement).

Signed-off-by: Kees Cook &lt;keescook@chromium.org&gt;
Reviewed-by: Casey Schaufler &lt;casey@schaufler-ca.com&gt;
Reviewed-by: John Johansen &lt;john.johansen@canonical.com&gt;
diff --git a/security/loadpin/Kconfig b/security/loadpin/Kconfig
@@ -10,10 +10,10 @@ config SECURITY_LOADPIN
 	  have a root filesystem backed by a read-only device such as
 	  dm-verity or a CDROM.
 
-config SECURITY_LOADPIN_ENABLED
+config SECURITY_LOADPIN_ENFORCE
 	bool "Enforce LoadPin at boot"
 	depends on SECURITY_LOADPIN
 	help
 	  If selected, LoadPin will enforce pinning at boot. If not
 	  selected, it can be enabled at boot with the kernel parameter
-	  "loadpin.enabled=1".
+	  "loadpin.enforce=1".
diff --git a/security/loadpin/loadpin.c b/security/loadpin/loadpin.c
@@ -44,7 +44,7 @@ static void report_load(const char *origin, struct file *file, char *operation)
 	kfree(pathname);
 }
 
-static int enabled = IS_ENABLED(CONFIG_SECURITY_LOADPIN_ENABLED);
+static int enforce = IS_ENABLED(CONFIG_SECURITY_LOADPIN_ENFORCE);
 static struct super_block *pinned_root;
 static DEFINE_SPINLOCK(pinned_root_spinlock);
 
@@ -60,8 +60,8 @@ static struct ctl_path loadpin_sysctl_path[] = {
 
 static struct ctl_table loadpin_sysctl_table[] = {
 	{
-		.procname       = "enabled",
-		.data           = &enabled,
+		.procname       = "enforce",
+		.data           = &enforce,
 		.maxlen         = sizeof(int),
 		.mode           = 0644,
 		.proc_handler   = proc_dointvec_minmax,
@@ -100,7 +100,7 @@ static void check_pinning_enforcement(struct super_block *mnt_sb)
 					   loadpin_sysctl_table))
 			pr_notice("sysctl registration failed!\n");
 		else
-			pr_info("load pinning can be disabled.\n");
+			pr_info("enforcement can be disabled.\n");
 	} else
 		pr_info("load pinning engaged.\n");
 }
@@ -131,7 +131,7 @@ static int loadpin_read_file(struct file *file, enum kernel_read_file_id id)
 
 	/* This handles the older init_module API that has a NULL file. */
 	if (!file) {
-		if (!enabled) {
+		if (!enforce) {
 			report_load(origin, NULL, "old-api-pinning-ignored");
 			return 0;
 		}
@@ -154,7 +154,7 @@ static int loadpin_read_file(struct file *file, enum kernel_read_file_id id)
 		 * Unlock now since it's only pinned_root we care about.
 		 * In the worst case, we will (correctly) report pinning
 		 * failures before we have announced that pinning is
-		 * enabled. This would be purely cosmetic.
+		 * enforcing. This would be purely cosmetic.
 		 */
 		spin_unlock(&pinned_root_spinlock);
 		check_pinning_enforcement(pinned_root);
@@ -164,7 +164,7 @@ static int loadpin_read_file(struct file *file, enum kernel_read_file_id id)
 	}
 
 	if (IS_ERR_OR_NULL(pinned_root) || load_root != pinned_root) {
-		if (unlikely(!enabled)) {
+		if (unlikely(!enforce)) {
 			report_load(origin, file, "pinning-ignored");
 			return 0;
 		}
@@ -189,10 +189,11 @@ static struct security_hook_list loadpin_hooks[] __lsm_ro_after_init = {
 
 void __init loadpin_add_hooks(void)
 {
-	pr_info("ready to pin (currently %sabled)", enabled ? "en" : "dis");
+	pr_info("ready to pin (currently %senforcing)\n",
+		enforce ? "" : "not ");
 	security_add_hooks(loadpin_hooks, ARRAY_SIZE(loadpin_hooks), "loadpin");
 }
 
 /* Should not be mutable after boot, so not listed in sysfs (perm == 0). */
-module_param(enabled, int, 0);
-MODULE_PARM_DESC(enabled, "Pin module/firmware loading (default: true)");
+module_param(enforce, int, 0);
+MODULE_PARM_DESC(enforce, "Enforce module/firmware pinning");
