USB: serial: fix hang when opening port

commit eba0e3c3a0ba7b96f01cbe997680f6a4401a0bfc upstream.

Johan's 'fix use-after-free in TIOCMIWAIT' patchset[1] introduces
one bug which can cause kernel hang when opening port.

This patch initialized the 'port->delta_msr_wait' waitqueue head
to fix the bug which is introduced in 3.9-rc4.

[1], http://marc.info/?l=linux-usb&m=136368139627876&w=2

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Acked-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
index 2482d5edc670f9b587ea8e711c14286d62d2604d..850faa44700009ab88bcfce8ea0785295e01d9f2 100644 (file)
--- a/drivers/usb/serial/usb-serial.c
+++ b/drivers/usb/serial/usb-serial.c
@@ -905,6 +905,7 @@ int usb_serial_probe(struct usb_interface *interface,
                port->port.ops = &serial_port_ops;
                port->serial = serial;
                spin_lock_init(&port->lock);
+               init_waitqueue_head(&port->delta_msr_wait);
                /* Keep this for private driver use for the moment but
                   should probably go away */
                INIT_WORK(&port->work, usb_serial_port_work);