In the Linux kernel, the following vulnerability has been resolved: tty: tty_port: restore TTY_IO_ERROR on activation failure Make sure to

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

tty: tty_port: restore TTY_IO_ERROR on activation failure

Make sure to restore the TTY_IO_ERROR flag if activation fails to
prevent I/O attempts on a port that is gone or powered down.

This specifically avoids issues like kernel panic due to unclocked
accesses or NULL-pointer dereferences when accessing powered down or
deregistered ports when a TTY ioctl races with hangup and open.

Note that the flag is set again in tty_port_close() but not restoring it
on activation failure leaves a window where drivers fail to handle the
ioctl-hangup race.