[PATCH net v3] mctp: check register_netdevice_notifier() error in mctp_device_init()

mctp_device_init() handles errors from rtnl_af_register() and
rtnl_register_many(), but ignores the return value of
register_netdevice_notifier(). If notifier registration fails, init can
still return success while the module is only partially initialized.

Check the notifier registration error and fail module init early.

Fixes: 583be982d934 ("mctp: Add device handling and netlink interface")
Signed-off-by: Minhong He <redacted>
---
v3:
- Correct Fixes tag to 583be982d934 (bug predates d51705614f66).
- No Cc:stable (unlikely init failure path; stable would also need
  d51705614f66 as a prereq on older trees).
v2: https://lore.kernel.org/netdev/20260716063534.116793-1-heminhong@kylinos.cn/ (local)
v1: https://lore.kernel.org/netdev/20260713073918.419422-1-heminhong@kylinos.cn/ (local)

 net/mctp/device.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/mctp/device.c b/net/mctp/device.c
index 2c84df674669..822120e860c8 100644
--- a/net/mctp/device.c
+++ b/net/mctp/device.c

@@ -536,7 +536,9 @@ int __init mctp_device_init(void)
 {
 	int err;
 
-	register_netdevice_notifier(&mctp_dev_nb);
+	err = register_netdevice_notifier(&mctp_dev_nb);
+	if (err)
+		return err;
 
 	err = rtnl_af_register(&mctp_af_ops);
 	if (err)

-- 
2.25.1