Laurent Bercot:
Of course, but once the fd is closed, /dev/console should not have any impact on the process, so would a kbrequest still reach it?
Yes. First: This is a kernel virtual terminal thing not a console thing. Strictly speaking, it is doing it wrongly to access it through the console device, which is not necessarily a KVT. Second: The mechanism does not require an open file descriptor. It requires that the target process never terminate, because there's no symmetrical kernel API function to disable the mechanism once it has been enabled, but it does not require that that process have any particular file descriptors open.
