CRED: Wrap task credential accesses in the MIPS arch

Wrap access to task credentials so that they can be separated more easily from
the task_struct during the introduction of COW creds.

Change most current->(|e|s|fs)[ug]id to current_(|e|s|fs)[ug]id().

Change some task->e?[ug]id to task_e?[ug]id().  In some places it makes more
sense to use RCU directly rather than a convenient wrapper; these will be
addressed by later patches.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Signed-off-by: James Morris <jmorris@namei.org>

arch/mips/kernel/mips-mt-fpaff.c

@@ -51,6 +51,7 @@ asmlinkage long mipsmt_sys_sched_setaffinity(pid_t pid, unsigned int len,
 	int retval;
 	struct task_struct *p;
 	struct thread_info *ti;
+	uid_t euid;
 
 	if (len < sizeof(new_mask))
 		return -EINVAL;
@@ -76,9 +77,9 @@ asmlinkage long mipsmt_sys_sched_setaffinity(pid_t pid, unsigned int len,
 	 */
 	get_task_struct(p);
 
+	euid = current_euid();
 	retval = -EPERM;
-	if ((current->euid != p->euid) && (current->euid != p->uid) &&
-			!capable(CAP_SYS_NICE)) {
+	if (euid != p->euid && euid != p->uid && !capable(CAP_SYS_NICE)) {
 		read_unlock(&tasklist_lock);
 		goto out_unlock;
 	}