tty: tty_port: restore TTY_IO_ERROR on activation failure

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.

Where it's fixed