lsm: introduce looping macros for the initialization code

There are three common for loop patterns in the LSM initialization code
to loop through the ordered LSM list and the registered "early" LSMs.
This patch implements these loop patterns as macros to help simplify the
code and reduce the chance for errors.

Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: John Johansen <john.johhansen@canonical.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

Author: pcmoore

security/lsm_init.c

@@ -32,6 +32,15 @@ static __initdata bool debug;
 			pr_info(__VA_ARGS__);				\
 	} while (0)
 
+#define lsm_order_for_each(iter)					\
+	for ((iter) = ordered_lsms; *(iter); (iter)++)
+#define lsm_for_each_raw(iter)						\
+	for ((iter) = __start_lsm_info;					\
+	     (iter) < __end_lsm_info; (iter)++)
+#define lsm_early_for_each_raw(iter)					\
+	for ((iter) = __start_early_lsm_info;				\
+	     (iter) < __end_early_lsm_info; (iter)++)
+
 static int lsm_append(const char *new, char **result);
 
 /* Save user chosen LSM */
@@ -96,9 +105,10 @@ static bool __init exists_ordered_lsm(struct lsm_info *lsm)
 {
 	struct lsm_info **check;
 
-	for (check = ordered_lsms; *check; check++)
+	lsm_order_for_each(check) {
 		if (*check == lsm)
 			return true;
+	}
 
 	return false;
 }
@@ -209,7 +219,7 @@ static void __init ordered_lsm_parse(const char *order, const char *origin)
 	char *sep, *name, *next;
 
 	/* LSM_ORDER_FIRST is always first. */
-	for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
+	lsm_for_each_raw(lsm) {
 		if (lsm->order == LSM_ORDER_FIRST)
 			append_ordered_lsm(lsm, "  first");
 	}
@@ -224,8 +234,7 @@ static void __init ordered_lsm_parse(const char *order, const char *origin)
 		 * if the selected one was separately disabled: disable
 		 * all non-matching Legacy Major LSMs.
 		 */
-		for (major = __start_lsm_info; major < __end_lsm_info;
-		     major++) {
+		lsm_for_each_raw(major) {
 			if ((major->flags & LSM_FLAG_LEGACY_MAJOR) &&
 			    strcmp(major->name, chosen_major_lsm) != 0) {
 				set_enabled(major, false);
@@ -241,7 +250,7 @@ static void __init ordered_lsm_parse(const char *order, const char *origin)
 	while ((name = strsep(&next, ",")) != NULL) {
 		bool found = false;
 
-		for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
+		lsm_for_each_raw(lsm) {
 			if (strcmp(lsm->name, name) == 0) {
 				if (lsm->order == LSM_ORDER_MUTABLE)
 					append_ordered_lsm(lsm, origin);
@@ -256,7 +265,7 @@ static void __init ordered_lsm_parse(const char *order, const char *origin)
 
 	/* Process "security=", if given. */
 	if (chosen_major_lsm) {
-		for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
+		lsm_for_each_raw(lsm) {
 			if (exists_ordered_lsm(lsm))
 				continue;
 			if (strcmp(lsm->name, chosen_major_lsm) == 0)
@@ -265,13 +274,13 @@ static void __init ordered_lsm_parse(const char *order, const char *origin)
 	}
 
 	/* LSM_ORDER_LAST is always last. */
-	for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
+	lsm_for_each_raw(lsm) {
 		if (lsm->order == LSM_ORDER_LAST)
 			append_ordered_lsm(lsm, "   last");
 	}
 
 	/* Disable all LSMs not in the ordered list. */
-	for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
+	lsm_for_each_raw(lsm) {
 		if (exists_ordered_lsm(lsm))
 			continue;
 		set_enabled(lsm, false);
@@ -290,13 +299,14 @@ static void __init report_lsm_order(void)
 	pr_info("initializing lsm=");
 
 	/* Report each enabled LSM name, comma separated. */
-	for (early = __start_early_lsm_info;
-	     early < __end_early_lsm_info; early++)
+	lsm_early_for_each_raw(early) {
 		if (is_enabled(early))
 			pr_cont("%s%s", first++ == 0 ? "" : ",", early->name);
-	for (lsm = ordered_lsms; *lsm; lsm++)
+	}
+	lsm_order_for_each(lsm) {
 		if (is_enabled(*lsm))
 			pr_cont("%s%s", first++ == 0 ? "" : ",", (*lsm)->name);
+	}
 
 	pr_cont("\n");
 }
@@ -343,8 +353,9 @@ static void __init ordered_lsm_init(void)
 	} else
 		ordered_lsm_parse(builtin_lsm_order, "builtin");
 
-	for (lsm = ordered_lsms; *lsm; lsm++)
+	lsm_order_for_each(lsm) {
 		lsm_prepare(*lsm);
+	}
 
 	report_lsm_order();
 
@@ -382,8 +393,9 @@ static void __init ordered_lsm_init(void)
 
 	lsm_early_cred((struct cred *) current->cred);
 	lsm_early_task(current);
-	for (lsm = ordered_lsms; *lsm; lsm++)
+	lsm_order_for_each(lsm) {
 		initialize_lsm(*lsm);
+	}
 }
 
 static bool match_last_lsm(const char *list, const char *lsm)
@@ -485,7 +497,7 @@ int __init early_security_init(void)
 {
 	struct lsm_info *lsm;
 
-	for (lsm = __start_early_lsm_info; lsm < __end_early_lsm_info; lsm++) {
+	lsm_early_for_each_raw(lsm) {
 		if (!lsm->enabled)
 			lsm->enabled = &lsm_enabled_true;
 		lsm_prepare(lsm);
@@ -512,7 +524,7 @@ int __init security_init(void)
 	 * Append the names of the early LSM modules now that kmalloc() is
 	 * available
 	 */
-	for (lsm = __start_early_lsm_info; lsm < __end_early_lsm_info; lsm++) {
+	lsm_early_for_each_raw(lsm) {
 		init_debug("  early started: %s (%s)\n", lsm->name,
 			   is_enabled(lsm) ? "enabled" : "disabled");
 		if (lsm->enabled)