OverlayFS performs upper-layer operations through inode-based security
hooks. Those hooks receive the upper inode and dentry, but not the mount
idmap used by the VFS operation.
The security layer cannot distinguish an identity-mapped upper from an
idmapped one or make the same ownership decision as the VFS. The VFS
layer already passes the idmap down into all relevant inode operations
so this just brings the security hooks to parity.
So pass the mount idmap through the create, link, symlink, mkdir, mknod,
and permission hooks. Update the in-tree security implementations and
non-VFS callers accordingly.
Signed-off-by: Daan De Meyer <daan@amutable.com>
Reviewed-by: Christian Brauner (Amutable) <brauner@kernel.org>
[PM: updated the commit description as discussed on-list]
Signed-off-by: Paul Moore <paul@paul-moore.com>
16959c469f