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

From: Eric W. Biederman
Date: Tue Sep 09 2008 - 14:25:18 EST

Chuck Lever <chuck.lever@xxxxxxxxxx> 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:

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.

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