ovl: use O_LARGEFILE in ovl_copy_up()

Open the lower file with O_LARGEFILE in ovl_copy_up().

Pass O_LARGEFILE unconditionally in ovl_copy_up_data() as it's purely for
catching 32-bit userspace dealing with a file large enough that it'll be
mishandled if the application isn't aware that there might be an integer
overflow.  Inside the kernel, there shouldn't be any problems.

Reported-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Cc: <stable@vger.kernel.org> # v3.18+

fs/overlayfs/copy_up.c

@@ -81,11 +81,11 @@ static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
 	if (len == 0)
 		return 0;
 
-	old_file = ovl_path_open(old, O_RDONLY);
+	old_file = ovl_path_open(old, O_LARGEFILE | O_RDONLY);
 	if (IS_ERR(old_file))
 		return PTR_ERR(old_file);
 
-	new_file = ovl_path_open(new, O_WRONLY);
+	new_file = ovl_path_open(new, O_LARGEFILE | O_WRONLY);
 	if (IS_ERR(new_file)) {
 		error = PTR_ERR(new_file);
 		goto out_fput;