vhost/vsock: Fix error handling in vhost_vsock_init()

Bugzilla: https://bugzilla.redhat.com/2160028

commit 7a4efe1
Author: Yuan Can <yuancan@huawei.com>
Date:   Tue Nov 8 10:17:05 2022 +0000

    vhost/vsock: Fix error handling in vhost_vsock_init()

    A problem about modprobe vhost_vsock failed is triggered with the
    following log given:

    modprobe: ERROR: could not insert 'vhost_vsock': Device or resource busy

    The reason is that vhost_vsock_init() returns misc_register() directly
    without checking its return value, if misc_register() failed, it returns
    without calling vsock_core_unregister() on vhost_transport, resulting the
    vhost_vsock can never be installed later.
    A simple call graph is shown as below:

     vhost_vsock_init()
       vsock_core_register() # register vhost_transport
       misc_register()
         device_create_with_groups()
           device_create_groups_vargs()
             dev = kzalloc(...) # OOM happened
       # return without unregister vhost_transport

    Fix by calling vsock_core_unregister() when misc_register() returns error.

    Fixes: 433fc58 ("VSOCK: Introduce vhost_vsock.ko")
    Signed-off-by: Yuan Can <yuancan@huawei.com>
    Message-Id: <20221108101705.45981-1-yuancan@huawei.com>
    Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
    Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
    Acked-by: Jason Wang <jasowang@redhat.com>

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>

Author: stefano-garzarella

drivers/vhost/vsock.c

@@ -964,7 +964,14 @@ static int __init vhost_vsock_init(void)
 				  VSOCK_TRANSPORT_F_H2G);
 	if (ret < 0)
 		return ret;
-	return misc_register(&vhost_vsock_misc);
+
+	ret = misc_register(&vhost_vsock_misc);
+	if (ret) {
+		vsock_core_unregister(&vhost_transport.transport);
+		return ret;
+	}
+
+	return 0;
 };
 
 static void __exit vhost_vsock_exit(void)