CRED: Wrap task credential accesses in the ROSE protocol

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-hams@vger.kernel.org
Signed-off-by: James Morris <jmorris@namei.org>

net/rose/af_rose.c

@@ -690,7 +690,7 @@ static int rose_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
 
 	source = &addr->srose_call;
 
-	user = ax25_findbyuid(current->euid);
+	user = ax25_findbyuid(current_euid());
 	if (user) {
 		rose->source_call = user->call;
 		ax25_uid_put(user);
@@ -791,7 +791,7 @@ static int rose_connect(struct socket *sock, struct sockaddr *uaddr, int addr_le
 			goto out_release;
 		}
 
-		user = ax25_findbyuid(current->euid);
+		user = ax25_findbyuid(current_euid());
 		if (!user) {
 			err = -EINVAL;
 			goto out_release;