Alternative for Storage permission I noticed that almost all apps request the Storage permission, and this is quite OK since they need to store stuff to function properly. But it's a bit bugging me that they have access to all of my data. Mainly because most apps need storage for their own files, and have nothing to do with my pics, songs, etc. So ideally I would like to grant apps the permission to write any amount of data to the storage, but that it cannot read/modify any other data.

Is there an alternative permission that grants access to write any file to the storage, but read and modify only files the app itself has created?
It's a little more subtle than that. The Storage permission does NOT give the app the ability to read and write everything on the device. It gives the app the ability to read and write things like SDCards and USB devices. It does NOT give the app the ability to read and write everything on the device's main storage (where apps put their databases by default).

The reason it doesn't restrict to the app's own files is that external storage is generally formatted with the FAT filesystem, which doesn't have any concept of file or directory level permissions. There's simply no way for Android to enforce the restriction of files. Further, since such storage is often removeable, even if the filesystem supported permissions, there would be nothing stopping you from taking the media out and using another computer to change said permissions.