[PATCH v1] xenbus: Unregister reboot notifier on init failure

[Yuho Choi <dbgh9129@xxxxxxxxx>]

xs_init() registers xs_reboot_nb before initializing XenStore
communications and starting xenwatch. If either operation fails, the
notifier remains registered and a later initialization attempt can hit a
duplicate registration.

Check the notifier registration result and unregister it on every
subsequent failure path.

Fixes: fd8aa9095a95 ("xen: optimize xenbus driver for multiple concurrent 
xenstore accesses")
Signed-off-by: Yuho Choi <dbgh9129@xxxxxxxxx>
---
 drivers/xen/xenbus/xenbus_xs.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c
index d1cca4acb6f3..62274d377b3a 100644
--- a/drivers/xen/xenbus/xenbus_xs.c
+++ b/drivers/xen/xenbus/xenbus_xs.c
@@ -915,19 +915,27 @@ int xs_init(void)
        int err;
        struct task_struct *task;
 
-       register_reboot_notifier(&xs_reboot_nb);
+       err = register_reboot_notifier(&xs_reboot_nb);
+       if (err)
+               return err;
 
        /* Initialize the shared memory rings to talk to xenstored */
        err = xb_init_comms();
        if (err)
-               return err;
+               goto err_unregister_reboot_notifier;
 
        task = kthread_run(xenwatch_thread, NULL, "xenwatch");
-       if (IS_ERR(task))
-               return PTR_ERR(task);
+       if (IS_ERR(task)) {
+               err = PTR_ERR(task);
+               goto err_unregister_reboot_notifier;
+       }
 
        /* shutdown watches for kexec boot */
        xs_reset_watches();
 
        return 0;
+
+err_unregister_reboot_notifier:
+       unregister_reboot_notifier(&xs_reboot_nb);
+       return err;
 }
-- 
2.43.0