btrfs: Check name_len before read in iterate_dir_item

Since iterate_dir_item checks name_len in its own way,
so use btrfs_is_name_len_valid not 'verify_dir_item' to make more strict
name_len check.
Signed-off-by: Su Yue <suy.fnst@cn.fujitsu.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ switched ENAMETOOLONG to EIO ]
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/send.c

@@ -1069,6 +1069,12 @@ static int iterate_dir_item(struct btrfs_root *root, struct btrfs_path *path,
 			}
 		}
 
+		ret = btrfs_is_name_len_valid(eb, path->slots[0],
+			  (unsigned long)(di + 1), name_len + data_len);
+		if (!ret) {
+			ret = -EIO;
+			goto out;
+		}
 		if (name_len + data_len > buf_len) {
 			buf_len = name_len + data_len;
 			if (is_vmalloc_addr(buf)) {