[ 3.5.y.z extended stable ] Patch "USB: mct_u232: fix use-after-free in TIOCMIWAIT" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    USB: mct_u232: fix use-after-free in TIOCMIWAIT

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 0d8de5efbaee7f79088ca47b19b0185c6390f1e7 Mon Sep 17 00:00:00 2001
From: Johan Hovold <jhovold at gmail.com>
Date: Tue, 19 Mar 2013 09:21:18 +0100
Subject: [PATCH] USB: mct_u232: fix use-after-free in TIOCMIWAIT

commit cf1d24443677a0758cfa88ca40f24858b89261c0 upstream.

Use the port wait queue and make sure to check the serial disconnected
flag before accessing private port data after waking up.

This is is needed as the private port data (including the wait queue
itself) can be gone when waking up after a disconnect.

Signed-off-by: Johan Hovold <jhovold at gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/usb/serial/mct_u232.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/usb/serial/mct_u232.c b/drivers/usb/serial/mct_u232.c
index 66b91d5..5f005cc 100644
--- a/drivers/usb/serial/mct_u232.c
+++ b/drivers/usb/serial/mct_u232.c
@@ -118,8 +118,6 @@ struct mct_u232_private {
 	unsigned char	     last_msr;      /* Modem Status Register */
 	unsigned int	     rx_flags;      /* Throttling flags */
 	struct async_icount  icount;
-	wait_queue_head_t    msr_wait;	/* for handling sleeping while waiting
-						for msr change to happen */
 };

 #define THROTTLED		0x01
@@ -399,7 +397,6 @@ static int mct_u232_startup(struct usb_serial *serial)
 	if (!priv)
 		return -ENOMEM;
 	spin_lock_init(&priv->lock);
-	init_waitqueue_head(&priv->msr_wait);
 	usb_set_serial_port_data(serial->port[0], priv);

 	init_waitqueue_head(&serial->port[0]->write_wait);
@@ -416,7 +413,6 @@ static int mct_u232_startup(struct usb_serial *serial)
 	return 0;
 } /* mct_u232_startup */

-
 static void mct_u232_release(struct usb_serial *serial)
 {
 	struct mct_u232_private *priv;
@@ -616,7 +612,7 @@ static void mct_u232_read_int_callback(struct urb *urb)
 		tty_kref_put(tty);
 	}
 #endif
-	wake_up_interruptible(&priv->msr_wait);
+	wake_up_interruptible(&port->delta_msr_wait);
 	spin_unlock_irqrestore(&priv->lock, flags);
 exit:
 	retval = usb_submit_urb(urb, GFP_ATOMIC);
@@ -827,13 +823,17 @@ static int  mct_u232_ioctl(struct tty_struct *tty,
 		cprev = mct_u232_port->icount;
 		spin_unlock_irqrestore(&mct_u232_port->lock, flags);
 		for ( ; ; ) {
-			prepare_to_wait(&mct_u232_port->msr_wait,
+			prepare_to_wait(&port->delta_msr_wait,
 					&wait, TASK_INTERRUPTIBLE);
 			schedule();
-			finish_wait(&mct_u232_port->msr_wait, &wait);
+			finish_wait(&port->delta_msr_wait, &wait);
 			/* see if a signal did it */
 			if (signal_pending(current))
 				return -ERESTARTSYS;
+
+			if (port->serial->disconnected)
+				return -EIO;
+
 			spin_lock_irqsave(&mct_u232_port->lock, flags);
 			cnow = mct_u232_port->icount;
 			spin_unlock_irqrestore(&mct_u232_port->lock, flags);
--
1.8.1.2