If you have shell access to your server, you can change file permissions recursively with the following commands.
For directories:
find /path/to/your/wordpress/install/ -type d -exec chmod 755 {} ;For files:
find /path/to/your/wordpress/install/ -type f -exec chmod 644 {} ;To do them both in current folder recursively:
find . -type f -exec chmod 644 {} ; && find . -type d -exec chmod 755 {} ;User correction:
chown -R www-data:www-data .Full combined permission correction for current WordPress root folder:
chown -R www-data:www-data . && find . -type f -exec chmod 644 {} ; && find . -type d -exec chmod 755 {};