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

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Date:	Wed, 10 Sep 2008 11:23:05 +0200
From:	Cedric Le Goater <clg@...ibm.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Chuck Lever <chuck.lever@...cle.com>,
	"Serge E. Hallyn" <serue@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Trond Myklebust <trond.myklebust@....uio.no>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux Containers <containers@...ts.osdl.org>,
	linux-nfs@...r.kernel.org
Subject: Re: [RFC][PATCH] sunrpc: fix oops in rpc_create() when the mount
 namespace is unshared

Eric W. Biederman wrote:
> Chuck Lever <chuck.lever@...cle.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.

the task exiting brings down the lockd thread and unregisters the lockd service 
with the portmapper. This is done with a rpc call which creates a client and a
request.

that's how I understand the code and the oops.


C.
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