[ 3.5.y.z extended stable ] Patch "USB: mos7840: 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: mos7840: 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 fa8fe19dc58608735c91365eec8ec66dc9897f05 Mon Sep 17 00:00:00 2001
From: Johan Hovold <jhovold at gmail.com>
Date: Tue, 19 Mar 2013 09:21:20 +0100
Subject: [PATCH] USB: mos7840: fix use-after-free in TIOCMIWAIT

commit a14430db686b8e459e1cf070a6ecf391515c9ab9 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/mos7840.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/serial/mos7840.c b/drivers/usb/serial/mos7840.c
index be5f09b..2727955 100644
--- a/drivers/usb/serial/mos7840.c
+++ b/drivers/usb/serial/mos7840.c
@@ -224,7 +224,6 @@ struct moschip_port {
 	char open;
 	char open_ports;
 	wait_queue_head_t wait_chase;	/* for handling sleeping while waiting for chase to finish */
-	wait_queue_head_t delta_msr_wait;	/* for handling sleeping while waiting for msr change to happen */
 	int delta_msr_cond;
 	struct async_icount icount;
 	struct usb_serial_port *port;	/* loop back to the owner of this object */
@@ -444,7 +443,7 @@ static void mos7840_handle_new_msr(struct moschip_port *port, __u8 new_msr)
 		}

 		mos7840_port->delta_msr_cond = 1;
-		wake_up_interruptible(&mos7840_port->delta_msr_wait);
+		wake_up_interruptible(&port->port->delta_msr_wait);
 	}
 }

@@ -1166,7 +1165,6 @@ static int mos7840_open(struct tty_struct *tty, struct usb_serial_port *port)

 	/* initialize our wait queues */
 	init_waitqueue_head(&mos7840_port->wait_chase);
-	init_waitqueue_head(&mos7840_port->delta_msr_wait);

 	/* initialize our icount structure */
 	memset(&(mos7840_port->icount), 0x00, sizeof(mos7840_port->icount));
@@ -2307,13 +2305,18 @@ static int mos7840_ioctl(struct tty_struct *tty,
 		while (1) {
 			/* interruptible_sleep_on(&mos7840_port->delta_msr_wait); */
 			mos7840_port->delta_msr_cond = 0;
-			wait_event_interruptible(mos7840_port->delta_msr_wait,
-						 (mos7840_port->
+			wait_event_interruptible(port->delta_msr_wait,
+						 (port->serial->disconnected ||
+						  mos7840_port->
 						  delta_msr_cond == 1));

 			/* see if a signal did it */
 			if (signal_pending(current))
 				return -ERESTARTSYS;
+
+			if (port->serial->disconnected)
+				return -EIO;
+
 			cnow = mos7840_port->icount;
 			smp_rmb();
 			if (cnow.rng == cprev.rng && cnow.dsr == cprev.dsr &&
--
1.8.1.2