LoadPin: report improvement and parameter renaming

- Report human-readable device name during init
 - Change boot parameter and Kconfig "enabled" to "enforce"
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 Comment: Kees Cook <kees@outflux.net>
 
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Merge tag 'loadpin-security-next' of https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux into next-loadpin

LoadPin: report improvement and parameter renaming

- Report human-readable device name during init
- Change boot parameter and Kconfig "enabled" to "enforce"

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".

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",
+		.procname       = "enforce",
-		.data           = &enabled,
+		.data           = &enforce,
 		.maxlen         = sizeof(int),
 		.mode           = 0644,
 		.proc_handler   = proc_dointvec_minmax,
@@ -84,8 +84,11 @@ static void check_pinning_enforcement(struct super_block *mnt_sb)
 	 * device, allow sysctl to change modes for testing.
 	 */
 	if (mnt_sb->s_bdev) {
+		char bdev[BDEVNAME_SIZE];
+
 		ro = bdev_read_only(mnt_sb->s_bdev);
-		pr_info("dev(%u,%u): %s\n",
+		bdevname(mnt_sb->s_bdev, bdev);
+		pr_info("%s (%u:%u): %s\n", bdev,
 			MAJOR(mnt_sb->s_bdev->bd_dev),
 			MINOR(mnt_sb->s_bdev->bd_dev),
 			ro ? "read-only" : "writable");
@@ -97,7 +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");
 }
@@ -128,7 +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;
 		}
@@ -151,7 +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);
@@ -161,7 +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;
 		}
@@ -186,10 +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_param(enforce, int, 0);
-MODULE_PARM_DESC(enabled, "Pin module/firmware loading (default: true)");
+MODULE_PARM_DESC(enforce, "Enforce module/firmware pinning");