Cannot delete files/directories that are not writable in lowerdir

[yuyichao]

ArchLinux, x86_64, kernel 5.14.7, latest git version of fuse-overlayfs

The following script attempts to delete two directory that are present in lowerdir owned by root.

mkdir -p {overlay,mount,upper,lower/v,lower/v2/A}
sudo chown -R root:root lower/{v,v2}
fuse-overlayfs -o "lowerdir=lower,upperdir=upper,workdir=overlay" "mount"

rm -rf "mount/v/"
rm -rf "mount/v2/"

It fails with

rm: cannot remove 'mount/v/': Operation not permitted
rm: cannot remove 'mount/v2/A': Permission denied

However, manually mknod in upper will cause the directory to be deleted (minus #324) so I think this could be supported.

[giuseppe]

when we copyup a directory we also copy the directory ownership, and that operation fails with EPERM since an unprivileged user cannot chown to root:root.

When you are using fuse-overlayfs in unprivileged mode you need to make sure the user has access to all the files, otherwise it is suggested to run in a user namespace (which is the main use case for fuse-overlayfs).