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

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Date:	Tue, 09 Sep 2008 13:08:29 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Chuck Lever <chuck.lever@...cle.com>
Cc:	"Serge E. Hallyn" <serue@...ibm.com>,
	Cedric Le Goater <clg@...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

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

> On Sep 9, 2008, at Sep 9, 2008, 2:20 PM, ebiederm@...ssion.com 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?
>
> cl_server is the server-side.  cl_nodename is the "machine name" of the client.

Thanks, Darn.  Looks like we need to capture both names at the same or a
similar point.

I'm wondering if we need to capture a network namespace as well.

>>> 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.
>
> It's worth investigating.  Just enable RPC tracing (/usr/sbin/rpcdebug -m rpc -s
> all) before shutting down the client.
>
> NFS unmounting is historically difficult because during a system shutdown,
> unmounting is the last thing to occur, and usually happens  after most system
> services (such as the portmapper service) have become unavailable.  That's fine
> for local file systems, but it makes  for a rather dodgy situation for NFS.

Interesting.

Eric

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