In the Linux kernel, the following vulnerability has been resolved:

m68k: nfcon: Do not call console_is_registered() in nfcon_device()

Since 7c2af0f634f1 ("tty: tty_io: use console_list_lock for list
synchronization") show_cons_active() calls the .device() method under
the console_list_lock, but console_is_registered() tries to acquire
console_list_lock as well, causing a deadlock.  It should not be
necessary to check console_is_registered() here since the function
should not be called in the fist place when the console is not
registered.