Kernel warning via unchecked NFS registration failure

Unchecked error handling in the Linux NFS client allows local users to trigger a kernel warning during network-namespace teardown. nfs_net_init accepts a failed rpc_proc_register call, so nfs_net_exit later asks remove_proc_entry to remove a proc directory that was never created. The path requires local low-privilege namespace operations after registration failure, and the public record documents a warning rather than a data effect.