In the Linux kernel, the following vulnerability has been resolved:
cxl/region: Block region delete during region creation
Expand the range lock, rename it regions_lock, to disable region deletion in the critical period between construct_region() and attach_target(), as well as the period between device_add() and registering the remove actions.
Otherwise, userspace can confuse the kernel. It can violate the assumption the region stays registered through the completion of cxl_add_to_region(). It can violate the assumption that devm_add_action_or_reset() is working with a live struct cxl_region.
It is ok for the region to disappear outside of those windows as that mirrors device hotplug flows where the proper locks are held.