[PATCH 050/102] USB: ssu100: fix use-after-free in TIOCMIWAIT

[Luis Henriques]

3.5.7.10 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Johan Hovold <jhovold at gmail.com>

commit 43a66b4c417ad15f6d2f632ce67ad195bdf999e8 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>
[ luis: backported to 3.5; adjust context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/usb/serial/ssu100.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/serial/ssu100.c b/drivers/usb/serial/ssu100.c
index c4409b1..3ad10b5 100644
--- a/drivers/usb/serial/ssu100.c
+++ b/drivers/usb/serial/ssu100.c
@@ -65,7 +65,6 @@ struct ssu100_port_private {
 	spinlock_t status_lock;
 	u8 shadowLSR;
 	u8 shadowMSR;
-	wait_queue_head_t delta_msr_wait; /* Used for TIOCMIWAIT */
 	struct async_icount icount;
 };
 
@@ -366,8 +365,9 @@ static int wait_modem_info(struct usb_serial_port *port, unsigned int arg)
 	spin_unlock_irqrestore(&priv->status_lock, flags);
 
 	while (1) {
-		wait_event_interruptible(priv->delta_msr_wait,
-					 ((priv->icount.rng != prev.rng) ||
+		wait_event_interruptible(port->delta_msr_wait,
+					 (port->serial->disconnected ||
+					  (priv->icount.rng != prev.rng) ||
 					  (priv->icount.dsr != prev.dsr) ||
 					  (priv->icount.dcd != prev.dcd) ||
 					  (priv->icount.cts != prev.cts)));
@@ -375,6 +375,9 @@ static int wait_modem_info(struct usb_serial_port *port, unsigned int arg)
 		if (signal_pending(current))
 			return -ERESTARTSYS;
 
+		if (port->serial->disconnected)
+			return -EIO;
+
 		spin_lock_irqsave(&priv->status_lock, flags);
 		cur = priv->icount;
 		spin_unlock_irqrestore(&priv->status_lock, flags);
@@ -455,7 +458,6 @@ static int ssu100_attach(struct usb_serial *serial)
 	}
 
 	spin_lock_init(&priv->status_lock);
-	init_waitqueue_head(&priv->delta_msr_wait);
 	usb_set_serial_port_data(port, priv);
 
 	return ssu100_initdevice(serial->dev);
@@ -536,7 +538,7 @@ static void ssu100_update_msr(struct usb_serial_port *port, u8 msr)
 			priv->icount.dcd++;
 		if (msr & UART_MSR_TERI)
 			priv->icount.rng++;
-		wake_up_interruptible(&priv->delta_msr_wait);
+		wake_up_interruptible(&port->delta_msr_wait);
 	}
 }
 
-- 
1.8.1.2