xen/blkfront: allow xenbus state transition to Closing->Closed when not Connected

This situation can occur when attempting to attach a block device whose
backend is an empty physical CD-ROM driver. The backend in this case
will go directly from the Initialising state to Closing->Closed.
Previously this would result in a NULL pointer deref on info->gd
(xenbus_dev_fatal does not return as a1a15ac5 seems to expect)

Cc: stable@kernel.org
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 8f905089b72b7e49c2434d1b6abba9fa76321051..6971a12e8b9b0ff4e9d9824e4298094381468a92 100644 (file)
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -977,8 +977,10 @@ static void backend_changed(struct xenbus_device *dev,
                break;
 
        case XenbusStateClosing:
-               if (info->gd == NULL)
-                       xenbus_dev_fatal(dev, -ENODEV, "gd is NULL");
+               if (info->gd == NULL) {
+                       xenbus_frontend_closed(dev);
+                       break;
+               }
                bd = bdget_disk(info->gd, 0);
                if (bd == NULL)
                        xenbus_dev_fatal(dev, -ENODEV, "bdget failed");