Here is the simple way to change the permission of all files or folders in a certain path.
In order to change the permission of all files use the below command.
sudo find . -type f -exec chmod 664 {} \;
This command will assign the permission of 664 to all the files in the current folder "f" that represents the files. The dot next to find represent the current directory path. If you want to change the permission of all files from a different directory then you need to add that directory path instead of a dot.
Search and change all folders permissions in Ubuntu
Same like files you can search and change the permissions of all folders by using the very similar command.
sudo find . -type d -exec chmod 775 {} \;
This command will assign 775 permission to all the folders under the current path. If you want to change the folder permissions of any other directory then you need to enter another directory path instead of a dot.