security: convert security hooks to use hlist

This changes security_hook_heads to use hlist_heads instead of
the circular doubly-linked list heads. This should cut down
the size of the struct by about half.

In addition, it allows mutation of the hooks at the tail of the
callback list without having to modify the head. The longer-term
purpose of this is to enable making the heads read only.

Signed-off-by: Sargun Dhillon <sargun@sargun.me>
Reviewed-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: James Morris <james.morris@microsoft.com>
diff --git a/security/security.c b/security/security.c
index 14c2919..dd246a3 100644
--- a/security/security.c
+++ b/security/security.c
@@ -61,11 +61,11 @@
 int __init security_init(void)
 {
 	int i;
-	struct list_head *list = (struct list_head *) &security_hook_heads;
+	struct hlist_head *list = (struct hlist_head *) &security_hook_heads;
 
-	for (i = 0; i < sizeof(security_hook_heads) / sizeof(struct list_head);
+	for (i = 0; i < sizeof(security_hook_heads) / sizeof(struct hlist_head);
 	     i++)
-		INIT_LIST_HEAD(&list[i]);
+		INIT_HLIST_HEAD(&list[i]);
 	pr_info("Security Framework initialized\n");
 
 	/*
@@ -163,7 +163,7 @@
 
 	for (i = 0; i < count; i++) {
 		hooks[i].lsm = lsm;
-		list_add_tail_rcu(&hooks[i].list, hooks[i].head);
+		hlist_add_tail_rcu(&hooks[i].list, hooks[i].head);
 	}
 	if (lsm_append(lsm, &lsm_names) < 0)
 		panic("%s - Cannot get early memory.\n", __func__);
@@ -201,7 +201,7 @@
 	do {							\
 		struct security_hook_list *P;			\
 								\
-		list_for_each_entry(P, &security_hook_heads.FUNC, list)	\
+		hlist_for_each_entry(P, &security_hook_heads.FUNC, list) \
 			P->hook.FUNC(__VA_ARGS__);		\
 	} while (0)
 
@@ -210,7 +210,7 @@
 	do {							\
 		struct security_hook_list *P;			\
 								\
-		list_for_each_entry(P, &security_hook_heads.FUNC, list) { \
+		hlist_for_each_entry(P, &security_hook_heads.FUNC, list) { \
 			RC = P->hook.FUNC(__VA_ARGS__);		\
 			if (RC != 0)				\
 				break;				\
@@ -317,7 +317,7 @@
 	 * agree that it should be set it will. If any module
 	 * thinks it should not be set it won't.
 	 */
-	list_for_each_entry(hp, &security_hook_heads.vm_enough_memory, list) {
+	hlist_for_each_entry(hp, &security_hook_heads.vm_enough_memory, list) {
 		rc = hp->hook.vm_enough_memory(mm, pages);
 		if (rc <= 0) {
 			cap_sys_admin = 0;
@@ -805,7 +805,7 @@
 	/*
 	 * Only one module will provide an attribute with a given name.
 	 */
-	list_for_each_entry(hp, &security_hook_heads.inode_getsecurity, list) {
+	hlist_for_each_entry(hp, &security_hook_heads.inode_getsecurity, list) {
 		rc = hp->hook.inode_getsecurity(inode, name, buffer, alloc);
 		if (rc != -EOPNOTSUPP)
 			return rc;
@@ -823,7 +823,7 @@
 	/*
 	 * Only one module will provide an attribute with a given name.
 	 */
-	list_for_each_entry(hp, &security_hook_heads.inode_setsecurity, list) {
+	hlist_for_each_entry(hp, &security_hook_heads.inode_setsecurity, list) {
 		rc = hp->hook.inode_setsecurity(inode, name, value, size,
 								flags);
 		if (rc != -EOPNOTSUPP)
@@ -1126,7 +1126,7 @@
 	int rc = -ENOSYS;
 	struct security_hook_list *hp;
 
-	list_for_each_entry(hp, &security_hook_heads.task_prctl, list) {
+	hlist_for_each_entry(hp, &security_hook_heads.task_prctl, list) {
 		thisrc = hp->hook.task_prctl(option, arg2, arg3, arg4, arg5);
 		if (thisrc != -ENOSYS) {
 			rc = thisrc;
@@ -1629,7 +1629,7 @@
 	 * For speed optimization, we explicitly break the loop rather than
 	 * using the macro
 	 */
-	list_for_each_entry(hp, &security_hook_heads.xfrm_state_pol_flow_match,
+	hlist_for_each_entry(hp, &security_hook_heads.xfrm_state_pol_flow_match,
 				list) {
 		rc = hp->hook.xfrm_state_pol_flow_match(x, xp, fl);
 		break;