It's possible to unplug usb device and do tiocmset() and tiocmget() without
valid interface in pl2303 module.

The patch below check this and return -ENODEV if interface was removed.

From: Flavio Leitner <fbl@conectiva.com.br>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff -purN linux-05-04-11/drivers/usb/serial/pl2303.c linux-05-04-11.usb/drivers/usb/serial/pl2303.c