Spurious files in a directory deleted in upper layer

[msimacek]

Given a directory structure:

/dir1/dir2/foo

when dir1 gets removed and then in another layer dir1 and dir1/dir2 get recreated, the file foo is not correctly hidden as it should be. This seems to be an extension of the problem reported in containers/podman#3021, which is marked as fixed, but it only seems to be fixed for the case when the file is in the deleted directory. When the file is in a subdirectory of the deleted directory, the issue is still present.

It can be reproduced using podman by building the following Dockerfile and checking for existence of the file foo using podman run as unpriviledged user.

FROM busybox

RUN mkdir -p /dir1/dir2
RUN touch /dir1/dir2/foo
RUN rm -r /dir1
RUN mkdir -p /dir1/dir2

There are actually two variants of the problem.

1. With the dockerfile above, the whole dir1 gets marked with a whiteout file.
2. When the above dockerfile is altered so that the last two RUN instructions are merged into one, dir1 gets marked as opaque (this only occurs when building with docker, not buildah).

fuse-overlayfs seems to handle both cases incorrectly, whereas kernel overlay works as expected (using podman as root or using docker)