LSM: Introduce enum lsm_order

In preparation for distinguishing the "capability" LSM from other LSMs, it
must be ordered first. This introduces LSM_ORDER_MUTABLE for the general
LSMs and LSM_ORDER_FIRST for capability. In the future LSM_ORDER_LAST
for could be added for anything that must run last (e.g. Landlock may
use this).

Signed-off-by: Kees Cook <keescook@chromium.org>
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 2849e9b..27d4db9 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -2045,8 +2045,14 @@ extern void security_add_hooks(struct security_hook_list *hooks, int count,
 #define LSM_FLAG_LEGACY_MAJOR	BIT(0)
 #define LSM_FLAG_EXCLUSIVE	BIT(1)
 
+enum lsm_order {
+	LSM_ORDER_FIRST = -1,	/* This is only for capabilities. */
+	LSM_ORDER_MUTABLE = 0,
+};
+
 struct lsm_info {
 	const char *name;	/* Required. */
+	enum lsm_order order;	/* Optional: default is LSM_ORDER_MUTABLE */
 	unsigned long flags;	/* Optional: flags describing LSM */
 	int *enabled;		/* Optional: controlled by CONFIG_LSM */
 	int (*init)(void);	/* Required. */