[PATCH] xen/privcmd: unregister xenstore notifier on module exit

[GuoHan Zhao]

Commit 453b8fb68f36 ("xen/privcmd: restrict usage in
unprivileged domU") added a xenstore notifier to defer setting the
restriction target until Xenstore is ready.

XEN_PRIVCMD can be built as a module, but privcmd_exit() leaves that
notifier behind. Balance the notifier lifecycle by unregistering it on
module exit.

This is harmless even if xenstore was already ready at registration
time and the notifier was never queued on the chain.

Fixes: 453b8fb68f3641fe ("xen/privcmd: restrict usage in unprivileged domU")
Signed-off-by: GuoHan Zhao <zhaoguohan@xxxxxxxxxx>
---
 drivers/xen/privcmd.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index bbf9ee21306c..15ba592236e8 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -1765,6 +1765,9 @@ static int __init privcmd_init(void)
 
 static void __exit privcmd_exit(void)
 {
+	if (!xen_initial_domain())
+		unregister_xenstore_notifier(&xenstore_notifier);
+
 	privcmd_ioeventfd_exit();
 	privcmd_irqfd_exit();
 	misc_deregister(&privcmd_dev);
-- 
2.43.0