Re: [RFC][PATCH] sunrpc: fix oops in rpc_create() when the mount namespace is unshared

[ebiederm@xmission.com (Eric W. Biederman)]

Chuck Lever <chuck.lever@oracle.com> writes:

> If the upper layers are responsible for providing the utsname, you will need to
> fix up lockd and the NFS server's callback client too, at  least.

Actually looking at the code.  It looks like a proper fix may be  even simpler.
Why do we have both clnt->cl_server and clnt->cl_nodename?    Or is cl_server
the other side of the connection?

>>> What are we trying to achieve by reading utsname?
>>
>> It looks like it gets copied into the sunrpc messages so I assume it is
>> a part of the sunrpc spec?
>
> It appears to be used only for RPC's AUTH_SYS credentials.  The nodename is used
> to identify the caller's host.  See RFC 1831,  Appendix A:
>
>   http://rfclibrary.hosting.com/rfc/rfc1831/rfc1831-16.asp

Thanks that helps a lot.

> I'm not terribly familiar with uts namespaces, though.  Can someone explain why
> we need to distinguish between these for AUTH_SYS if the  caller is on a remote
> system?

Semantically processes in different uts namespaces are on different machines.

> I don't like the idea of an oops in here.  Instead, (for now) it should warn and
> fail to create the client, IMO.

Which is interesting when the problem happens during NFS unmount.  Although
frankly it could fail anyway.

It seems strange that we are creating a client during unmount anyway.

Eric