USB: disconnect open race in legousbtower

again, possible use after free due to touching intfdata without lock.

Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/misc/legousbtower.c b/drivers/usb/misc/legousbtower.c
index 561970b..aab3200 100644 (file)
--- a/drivers/usb/misc/legousbtower.c
+++ b/drivers/usb/misc/legousbtower.c
@@ -198,6 +198,7 @@ static struct usb_device_id tower_table [] = {
 };
 
 MODULE_DEVICE_TABLE (usb, tower_table);
+static DEFINE_MUTEX(open_disc_mutex);
 
 #define LEGO_USB_TOWER_MINOR_BASE      160
 
@@ -350,25 +351,31 @@ static int tower_open (struct inode *inode, struct file *file)
                goto exit;
        }
 
+       mutex_lock(&open_disc_mutex);
        dev = usb_get_intfdata(interface);
 
        if (!dev) {
+               mutex_unlock(&open_disc_mutex);
                retval = -ENODEV;
                goto exit;
        }
 
        /* lock this device */
        if (down_interruptible (&dev->sem)) {
+               mutex_unlock(&open_disc_mutex);
                retval = -ERESTARTSYS;
                goto exit;
        }
 
+
        /* allow opening only once */
        if (dev->open_count) {
+               mutex_unlock(&open_disc_mutex);
                retval = -EBUSY;
                goto unlock_exit;
        }
        dev->open_count = 1;
+       mutex_unlock(&open_disc_mutex);
 
        /* reset the tower */
        result = usb_control_msg (dev->udev,
@@ -437,9 +444,10 @@ static int tower_release (struct inode *inode, struct file *file)
        if (dev == NULL) {
                dbg(1, "%s: object is NULL", __FUNCTION__);
                retval = -ENODEV;
-               goto exit;
+               goto exit_nolock;
        }
 
+       mutex_lock(&open_disc_mutex);
        if (down_interruptible (&dev->sem)) {
                retval = -ERESTARTSYS;
                goto exit;
@@ -468,6 +476,8 @@ unlock_exit:
        up (&dev->sem);
 
 exit:
+       mutex_unlock(&open_disc_mutex);
+exit_nolock:
        dbg(2, "%s: leave, return value %d", __FUNCTION__, retval);
        return retval;
 }
@@ -989,6 +999,7 @@ static void tower_disconnect (struct usb_interface *interface)
        dbg(2, "%s: enter", __FUNCTION__);
 
        dev = usb_get_intfdata (interface);
+       mutex_lock(&open_disc_mutex);
        usb_set_intfdata (interface, NULL);
 
        minor = dev->minor;
@@ -997,6 +1008,7 @@ static void tower_disconnect (struct usb_interface *interface)
        usb_deregister_dev (interface, &tower_class);
 
        down (&dev->sem);
+       mutex_unlock(&open_disc_mutex);
 
        /* if the device is not opened, then we clean up right now */
        if (!dev->open_count) {