TOMOYO: Abstract use of cred security blob

Don't use the cred->security pointer directly.
Provide helper functions that provide the security blob pointer.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
[kees: adjusted for ordered init series]
Signed-off-by: Kees Cook <keescook@chromium.org>
diff --git a/security/tomoyo/securityfs_if.c b/security/tomoyo/securityfs_if.c
index 1d3d7e7..768dff9 100644
--- a/security/tomoyo/securityfs_if.c
+++ b/security/tomoyo/securityfs_if.c
@@ -71,9 +71,12 @@ static ssize_t tomoyo_write_self(struct file *file, const char __user *buf,
 				if (!cred) {
 					error = -ENOMEM;
 				} else {
-					struct tomoyo_domain_info *old_domain =
-						cred->security;
-					cred->security = new_domain;
+					struct tomoyo_domain_info **blob;
+					struct tomoyo_domain_info *old_domain;
+
+					blob = tomoyo_cred(cred);
+					old_domain = *blob;
+					*blob = new_domain;
 					atomic_inc(&new_domain->users);
 					atomic_dec(&old_domain->users);
 					commit_creds(cred);
@@ -234,10 +237,14 @@ static void __init tomoyo_create_entry(const char *name, const umode_t mode,
  */
 static int __init tomoyo_initerface_init(void)
 {
+	struct tomoyo_domain_info *domain;
 	struct dentry *tomoyo_dir;
 
+	if (!tomoyo_enabled)
+		return 0;
+	domain = tomoyo_domain();
 	/* Don't create securityfs entries unless registered. */
-	if (current_cred()->security != &tomoyo_kernel_domain)
+	if (domain != &tomoyo_kernel_domain)
 		return 0;
 
 	tomoyo_dir = securityfs_create_dir("tomoyo", NULL);