USB: serial: ftdi_sio: Handle the old_termios == 0 case e.g. uart_resume_port()

commit c515598e upstream.

  Handle null old_termios in ftdi_set_termios() calls from uart_resume_port().
Signed-off-by: Andrew Worsley <amworsley@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/usb/serial/ftdi_sio.c

@@ -2169,6 +2169,9 @@ static void ftdi_set_termios(struct tty_struct *tty,
 
 	cflag = termios->c_cflag;
 
+	if (old_termios == 0)
+		goto no_skip;
+
 	if (old_termios->c_cflag == termios->c_cflag
 	    && old_termios->c_ispeed == termios->c_ispeed
 	    && old_termios->c_ospeed == termios->c_ospeed)
@@ -2182,6 +2185,7 @@ static void ftdi_set_termios(struct tty_struct *tty,
 	    (termios->c_cflag & (CSIZE|PARODD|PARENB|CMSPAR|CSTOPB)))
 		goto no_data_parity_stop_changes;
 
+no_skip:
 	/* Set number of data bits, parity, stop bits */
 
 	urb_value = 0;