IMA: use list_splice_tail_init_rcu() instead of its open coded variant

Use list_splice_tail_init_rcu() to extend the existing custom IMA policy
with additional IMA policy rules.
Signed-off-by: NPetko Manolov <petko.manolov@konsulko.com>
Signed-off-by: NMimi Zohar <zohar@linux.vnet.ibm.com>

security/integrity/ima/ima_policy.c

@@ -527,22 +527,9 @@ int ima_check_policy(void)
  */
 void ima_update_policy(void)
 {
-	struct list_head *first, *last, *policy;
+	struct list_head *policy = &ima_policy_rules;
 
-	/* append current policy with the new rules */
-	first = (&ima_temp_rules)->next;
-	last = (&ima_temp_rules)->prev;
-	policy = &ima_policy_rules;
-
-	synchronize_rcu();
-
-	last->next = policy;
-	rcu_assign_pointer(list_next_rcu(policy->prev), first);
-	first->prev = policy->prev;
-	policy->prev = last;
-
-	/* prepare for the next policy rules addition */
-	INIT_LIST_HEAD(&ima_temp_rules);
+	list_splice_tail_init_rcu(&ima_temp_rules, policy, synchronize_rcu);
 
 	if (ima_rules != policy) {
 		ima_policy_flag = 0;