WordPress requires the permission to access your webpage server to perform the requested operation on the WordPress installation topic.

First, modify the WordPress permission. You must have the write permission:
Chmod-r 755/var/www/WordPress
Explanation: chmod is the command for modifying the file (folder) Permission. Here, an R parameter is added, that is, all files (folders) in the/var/www/WordPress folder) to 755.
Chown-R

Apache/Var/www/WordPress
Explanation: chown is a command used to modify a file (folder) User Group. The parameter r serves the same purpose as CHMOD. However, you must have the root permission to execute this command.

In this case, assume that your PHP user group is Apache. After modification, try the automatic WP upgrade. The one-click upgrade will proceed smoothly.

View user groups:

PS-Ef | grep httpd