uwb: init beacon cache entry before registering uwb device

commit 675f0ab2 upstream.

Make sure the uwb_dev->bce entry is set before calling uwb_dev_add in
uwbd_dev_onair so that usermode will only see the device after it is
properly initialized.  This fixes a kernel panic that can occur if
usermode tries to access the IEs sysfs attribute of a UWB device before
the driver has had a chance to set the beacon cache entry.
Signed-off-by: Thomas Pugliese <thomas.pugliese@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/uwb/lc-dev.c

@@ -441,16 +441,19 @@ void uwbd_dev_onair(struct uwb_rc *rc, struct uwb_beca_e *bce)
 	uwb_dev->mac_addr = *bce->mac_addr;
 	uwb_dev->dev_addr = bce->dev_addr;
 	dev_set_name(&uwb_dev->dev, macbuf);
+
+	/* plug the beacon cache */
+	bce->uwb_dev = uwb_dev;
+	uwb_dev->bce = bce;
+	uwb_bce_get(bce);		/* released in uwb_dev_sys_release() */
+
 	result = uwb_dev_add(uwb_dev, &rc->uwb_dev.dev, rc);
 	if (result < 0) {
 		dev_err(dev, "new device %s: cannot instantiate device\n",
 			macbuf);
 		goto error_dev_add;
 	}
-	/* plug the beacon cache */
-	bce->uwb_dev = uwb_dev;
-	uwb_dev->bce = bce;
-	uwb_bce_get(bce);		/* released in uwb_dev_sys_release() */
+
 	dev_info(dev, "uwb device (mac %s dev %s) connected to %s %s\n",
 		 macbuf, devbuf, rc->uwb_dev.dev.parent->bus->name,
 		 dev_name(rc->uwb_dev.dev.parent));
@@ -458,6 +461,8 @@ void uwbd_dev_onair(struct uwb_rc *rc, struct uwb_beca_e *bce)
 	return;
 
 error_dev_add:
+	bce->uwb_dev = NULL;
+	uwb_bce_put(bce);
 	kfree(uwb_dev);
 	return;
 }