Issue while Upgrading from 12.0.0 to 12.0.1

Hello,
I copied the files of 12.0.1 to the web root directory of my OS, Linux. After copying the file, when I tried to login via Admin, only ERROR message is displayed. When I checked the log file, I noticed error /path-to-web/projeqtor/db/maintenance.php' at line (90). cause = fopen(../files/cron/MIGRATION): Failed to open stream: Permission denied. 
The owner and group of projeqtor dir is root and www-data respectively. 

Please help, 
Thanks & Regards,
Kishore

if(file_exists("../files/cron/MIGRATION")){
echo '<div class="messageERROR">'.i18n("messageUpgradeMigration").'</div>';
Above is the line from the maintenance.php.
After seeing the above line, I am guessing that since I have configured the entire "files" folder outside the projeqtor folder, I am getting this error. I guess subsequent lines would also fail.
I feel upgrade script should read the files path from the parameters.php and then should start upgrading accordingly.

Please advise.
Regards,
Kishore

Hi,
The issue is resolved. The problem was in providing the required access rights to read / write the files and folders.

Thanks,
Kishore