Fixing 500 OOPS: vsftpd: refusing to run with writable root inside chroot ()

After I upgrade my vsftp to newest version. I find I could not log in my vsftp as follow error:

500 OOPS: vsftpd: refusing to run with writable root inside chroot ()

This is becasue the new added feature of upgrade:

- Add stronger checks for the configuration error of running with a writeable root directory inside a chroot(). This may bite people who carelessly turned on chroot_local_user but such is life.

To fix this problem you should remove write permissions on the users root directory

chmod a-w /www/ftp

or
For the standard vsFTPd build (vsftpd): (still error for upload file)

allow_writeable_chroot=YES