CRED: Wrap current->cred and a few other accessors

Wrap current->cred and a few other accessors to hide their actual
implementation.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index b0904cd..ce8ac60 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -582,7 +582,7 @@
 {
 	struct request_key_auth *rka;
 	struct task_struct *t = current;
-	struct cred *cred = t->cred;
+	struct cred *cred = current_cred();
 	struct key *key;
 	key_ref_t key_ref, skey_ref;
 	int ret;