LSM: Build ordered list of LSMs to initialize

This constructs an ordered list of LSMs to initialize, using a hard-coded
list of only "integrity": minor LSMs continue to have direct hook calls,
and major LSMs continue to initialize separately.

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

1 files changed, 53 insertions, 5 deletions

diff --git a/security/security.c b/security/security.c
index c900d7a1441a..3a277fbf6023 100644
--- a/security/security.c
+++ b/security/security.c
@@ -37,6 +37,9 @@
 /* Maximum number of letters for an LSM name string */
 #define SECURITY_NAME_MAX       10
 
+/* How many LSMs were built into the kernel? */
+#define LSM_COUNT (__end_lsm_info - __start_lsm_info)
+
 struct security_hook_heads security_hook_heads __lsm_ro_after_init;
 static ATOMIC_NOTIFIER_HEAD(lsm_notifier_chain);
 
@@ -45,6 +48,9 @@ char *lsm_names;
 static __initdata char chosen_lsm[SECURITY_NAME_MAX + 1] =
         CONFIG_DEFAULT_SECURITY;
 
+/* Ordered list of LSMs to initialize. */
+static __initdata struct lsm_info **ordered_lsms;
+
 static __initdata bool debug;
 #define init_debug(...)                                         \
         do {                                                    \
@@ -85,6 +91,34 @@ static void __init set_enabled(struct lsm_info *lsm, bool enabled)
         }
 }
 
+/* Is an LSM already listed in the ordered LSMs list? */
+static bool __init exists_ordered_lsm(struct lsm_info *lsm)
+{
+        struct lsm_info **check;
+
+        for (check = ordered_lsms; *check; check++)
+                if (*check == lsm)
+                        return true;
+
+        return false;
+}
+
+/* Append an LSM to the list of ordered LSMs to initialize. */
+static int last_lsm __initdata;
+static void __init append_ordered_lsm(struct lsm_info *lsm, const char *from)
+{
+        /* Ignore duplicate selections. */
+        if (exists_ordered_lsm(lsm))
+                return;
+
+        if (WARN(last_lsm == LSM_COUNT, "%s: out of LSM slots!?\n", from))
+                return;
+
+        ordered_lsms[last_lsm++] = lsm;
+        init_debug("%s ordering: %s (%sabled)\n", from, lsm->name,
+                   is_enabled(lsm) ? "en" : "dis");
+}
+
 /* Is an LSM allowed to be initialized? */
 static bool __init lsm_allowed(struct lsm_info *lsm)
 {
@@ -121,18 +155,32 @@ static void __init maybe_initialize_lsm(struct lsm_info *lsm)
         }
 }
 
-static void __init ordered_lsm_init(void)
+/* Populate ordered LSMs list from single LSM name. */
+static void __init ordered_lsm_parse(const char *order, const char *origin)
 {
         struct lsm_info *lsm;
 
         for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
-                if ((lsm->flags & LSM_FLAG_LEGACY_MAJOR) != 0)
-                        continue;
-
-                maybe_initialize_lsm(lsm);
+                if (strcmp(lsm->name, order) == 0)
+                        append_ordered_lsm(lsm, origin);
         }
 }
 
+static void __init ordered_lsm_init(void)
+{
+        struct lsm_info **lsm;
+
+        ordered_lsms = kcalloc(LSM_COUNT + 1, sizeof(*ordered_lsms),
+                                GFP_KERNEL);
+
+        ordered_lsm_parse("integrity", "builtin");
+
+        for (lsm = ordered_lsms; *lsm; lsm++)
+                maybe_initialize_lsm(*lsm);
+
+        kfree(ordered_lsms);
+}
+
 static void __init major_lsm_init(void)
 {
         struct lsm_info *lsm;