xen-netfront: avoid crashing on resume after a failure in talk_to_netback()

commit d86b5672b1adb98b4cdd6fbf0224bbfb03db6e2e upstream.

Unavoidable crashes in netfront_resume() and netback_changed() after a
previous fail in talk_to_netback() (e.g. when we fail to read MAC from
xenstore) were discovered. The failure path in talk_to_netback() does
unregister/free for netdev but we don't reset drvdata and we try accessing
it after resume.

Fix the bug by removing the whole xen device completely with
device_unregister(), this guarantees we won't have any calls into netfront
after a failure.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 265e209..8d498a9 100644 (file)
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -1958,8 +1958,7 @@ abort_transaction_no_dev_fatal:
        xennet_disconnect_backend(info);
        xennet_destroy_queues(info);
  out:
-       unregister_netdev(info->netdev);
-       xennet_free_netdev(info->netdev);
+       device_unregister(&dev->dev);
        return err;
 }