ridmap indicates that the id mapping should be applied recursively (only
really relevant for rbind mount entries), and idmap indicates that it
should not be applied recursively (the default). If no mappings are
specified for the mount, we use the userns configuration of the
container. This matches the behaviour in the currently-unreleased
runtime-spec.
This includes a minor change to the state.json serialisation format, but
because there has been no released version of runc with commit
fbf183c6f8 ("Add uid and gid mappings to mounts"), we can safely make
this change without affecting running containers. Doing it this way
makes it much easier to handle m.IsIDMapped() and indicating that a
mapping has been specified.
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
With the rework of nsexec.c to handle MOUNT_ATTR_IDMAP in our Go code we
can now handle arbitrary mappings without issue, so remove the primary
artificial limit of mappings (must use the same mapping as the
container's userns) and add some tests.
We still only support idmap mounts for bind-mounts because configuring
mappings for other filesystems would require switching our entire mount
machinery to the new mount API. The current design would easily allow
for this but we would need to convert new mount options entirely to the
fsopen/fsconfig/fsmount API. This can be done in the future.
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Previously, all of our userns tests worked around the remapping issue by
creating the paths that runc would attempt to create (like /proc).
However, this isn't really accurate to how real userns containers are
created, so it's much better to actually remap the rootfs.
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
The idea was to make them strict on dest path from the beginning for
idmap mounts, as runc would do that for all mounts in the future. But
that is causing too many problems.
For now, let's just allow relative paths for idmap mounts too. It just
seems safer.
Signed-off-by: Rodrigo Campos <rodrigoca@microsoft.com>
Aleksa Sarai