CRED: Wrap task credential accesses in the core kernel

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>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-audit@redhat.com
Cc: containers@lists.linux-foundation.org
Cc: linux-mm@kvack.org
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/mm/shmem.c b/mm/shmem.c
index 0ed0752..f1b0d48 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1513,8 +1513,8 @@
 	inode = new_inode(sb);
 	if (inode) {
 		inode->i_mode = mode;
-		inode->i_uid = current->fsuid;
-		inode->i_gid = current->fsgid;
+		inode->i_uid = current_fsuid();
+		inode->i_gid = current_fsgid();
 		inode->i_blocks = 0;
 		inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
 		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
@@ -2278,8 +2278,8 @@
 	sbinfo->max_blocks = 0;
 	sbinfo->max_inodes = 0;
 	sbinfo->mode = S_IRWXUGO | S_ISVTX;
-	sbinfo->uid = current->fsuid;
-	sbinfo->gid = current->fsgid;
+	sbinfo->uid = current_fsuid();
+	sbinfo->gid = current_fsgid();
 	sbinfo->mpol = NULL;
 	sb->s_fs_info = sbinfo;