CRED: Separate task security context from task_struct

Separate the task security context from task_struct.  At this point, the
security data is temporarily embedded in the task_struct with two pointers
pointing to it.

Note that the Alpha arch is altered as it refers to (E)UID and (E)GID in
entry.S via asm-offsets.

With comment fixes Signed-off-by: Marc Dionne <marc.c.dionne@gmail.com>

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/mm/mempolicy.c b/mm/mempolicy.c
index 07a9647..b23492e 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1110,12 +1110,12 @@
 		const unsigned long __user *old_nodes,
 		const unsigned long __user *new_nodes)
 {
+	struct cred *cred, *tcred;
 	struct mm_struct *mm;
 	struct task_struct *task;
 	nodemask_t old;
 	nodemask_t new;
 	nodemask_t task_nodes;
-	uid_t uid, euid;
 	int err;
 
 	err = get_nodes(&old, old_nodes, maxnode);
@@ -1145,10 +1145,10 @@
 	 * capabilities, superuser privileges or the same
 	 * userid as the target process.
 	 */
-	uid = current_uid();
-	euid = current_euid();
-	if (euid != task->suid && euid != task->uid &&
-	    uid  != task->suid && uid  != task->uid &&
+	cred = current->cred;
+	tcred = task->cred;
+	if (cred->euid != tcred->suid && cred->euid != tcred->uid &&
+	    cred->uid  != tcred->suid && cred->uid  != tcred->uid &&
 	    !capable(CAP_SYS_NICE)) {
 		err = -EPERM;
 		goto out;