appletalk: Set error code if register_snap_client failed

commit c93ad1337ad06a718890a89cdd85188ff9a5a5cc upstream.

If register_snap_client fails in atalk_init,
error code should be set, otherwise it will
triggers NULL pointer dereference while unloading
module.

Fixes: 9804501fa122 ("appletalk: Fix potential NULL pointer dereference in unregister_snap_client")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/appletalk/ddp.c b/net/appletalk/ddp.c
index d9fdc75..93209c0 100644
--- a/net/appletalk/ddp.c
+++ b/net/appletalk/ddp.c
@@ -1927,6 +1927,7 @@
 	ddp_dl = register_snap_client(ddp_snap_id, atalk_rcv);
 	if (!ddp_dl) {
 		pr_crit("Unable to register DDP with SNAP.\n");
+		rc = -ENOMEM;
 		goto out_sock;
 	}