[Xen-devel] [PATCH]: Unregister inetdev notifiers on failure

[Chris Lalancette <clalance@xxxxxxxxxx>]

(Kier, I'm not sure if you are still accepting patches for the
linux-2.6.18-xen.hg tree, but if so...)

If you attempt to modprobe the pv-on-hvm netfront driver on a machine not
running under Xen (say, bare-metal, or under another hypervisor), the netfront
code correctly returns an ENODEV and fails to load.  However, if you then
shutdown that machine, you will oops while tearing down the network.  This is
because we forget to unregister the the inetaddr_notifier on failure, and so the
kernel takes a fatal page fault.  The attached patch just unregisters the
notifier on failure, and solves the problem for me.

Signed-off-by: Chris Lalancette <clalance@xxxxxxxxxx>

diff --git a/drivers/xen/netfront/netfront.c b/drivers/xen/netfront/netfront.c
--- a/drivers/xen/netfront/netfront.c
+++ b/drivers/xen/netfront/netfront.c
@@ -2199,6 +2199,8 @@ static struct xenbus_driver netfront_dri
 
 static int __init netif_init(void)
 {
+       int err;
+
        if (!is_running_on_xen())
                return -ENODEV;
 
@@ -2220,7 +2222,13 @@ static int __init netif_init(void)
        (void)register_inetaddr_notifier(&notifier_inetdev);
 #endif
 
-       return xenbus_register_frontend(&netfront_driver);
+       err = xenbus_register_frontend(&netfront_driver);
+       if (err) {
+#ifdef CONFIG_INET
+               unregister_inetaddr_notifier(&notifier_inetdev);
+#endif
+       }
+       return err;
 }
 module_init(netif_init);
 

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