eCryptfs: Copy lower inode attrs before dentry instantiation

Copies the lower inode attributes to the upper inode before passing the
upper inode to d_instantiate().  This is important for
security_d_instantiate().

The problem was discovered by a user seeing SELinux denials like so:

type=AVC msg=audit(1236812817.898:47): avc:  denied  { 0x100000 } for
pid=3584 comm="httpd" name="testdir" dev=ecryptfs ino=943872
scontext=root:system_r:httpd_t:s0
tcontext=root:object_r:httpd_sys_content_t:s0 tclass=file

Notice target class is file while testdir is really a directory,
confusing the permission translation (0x100000) due to the wrong i_mode.
Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>

fs/ecryptfs/main.c

@@ -190,14 +190,14 @@ int ecryptfs_interpose(struct dentry *lower_dentry, struct dentry *dentry,
 		init_special_inode(inode, lower_inode->i_mode,
 				   lower_inode->i_rdev);
 	dentry->d_op = &ecryptfs_dops;
-	if (flags & ECRYPTFS_INTERPOSE_FLAG_D_ADD)
-		d_add(dentry, inode);
-	else
-		d_instantiate(dentry, inode);
 	fsstack_copy_attr_all(inode, lower_inode, NULL);
 	/* This size will be overwritten for real files w/ headers and
 	 * other metadata */
 	fsstack_copy_inode_size(inode, lower_inode);
+	if (flags & ECRYPTFS_INTERPOSE_FLAG_D_ADD)
+		d_add(dentry, inode);
+	else
+		d_instantiate(dentry, inode);
 out:
 	return rc;
 }