Re: [RFC][PATCH 2/4] sunrpc: Use utsnamespaces

From: "J. Bruce Fields" <bfields@fieldses.org>
To: "Serge E. Hallyn" <serue@us.ibm.com>
Cc: Matt Helsley <matthltc@us.ibm.com>,
	Linux Containers <containers@lists.linux-foundation.org>,
	linux-nfs@vger.kernel.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Trond Myklebust <trond.myklebust@fys.uio.no>,
	Chuck Lever <chuck.lever@oracle.com>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Linux Containers <containers@lists.osdl.org>,
	Cedric Le Goater <clg@fr.ibm.com>
Subject: Re: [RFC][PATCH 2/4] sunrpc: Use utsnamespaces
Date: Tue, 6 Jan 2009 15:20:46 -0500	[thread overview]
Message-ID: <20090106202046.GF5901@fieldses.org> (raw)
In-Reply-To: <20090106200229.GA17031@us.ibm.com>

On Tue, Jan 06, 2009 at 02:02:29PM -0600, Serge E. Hallyn wrote:
> Quoting Matt Helsley (matthltc@us.ibm.com):
> > We can often specify the UTS namespace to use when starting an RPC client.
> > However sometimes no UTS namespace is available (specifically during system
> > shutdown as the last NFS mount in a container is unmounted) so fall
> > back to the initial UTS namespace.
> 
> So what happens if we take this patch and do nothing else?
> 
> The only potential problem situation will be rpc requests
> made on behalf of a container in which the last task has
> exited, right?  So let's say a container did an nfs mount
> and then exits, causing an nfs umount request.
> 
> That umount request will now be sent with the wrong nodename.
> Does that actually cause problems, will the server use the
> nodename to try and determine the client sending the request?

This is just the machine name in the auth_unix credential?  The linux
server ignores that completely (for the purpose of auth_unix
authenication, it identifies clients only by source ip address).  I
suspect other servers also ignore it, but I don't know.

--b.

> 
> thanks,
> -serge
> 
> > Signed-off-by: Matt Helsley <matthltc@us.ibm.com>
> > Cc: Cedric Le Goater <clg@fr.ibm.com>
> > Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
> > Cc: linux-nfs@vger.kernel.org
> > Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
> > Cc: Chuck Lever <chuck.lever@oracle.com>
> > Cc: Eric W. Biederman <ebiederm@xmission.com>
> > Cc: Linux Containers <containers@lists.osdl.org>
> > 
> > ---
> >  net/sunrpc/clnt.c |    7 +++++--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> > 
> > Index: linux-2.6.28/net/sunrpc/clnt.c
> > ===================================================================
> > --- linux-2.6.28.orig/net/sunrpc/clnt.c
> > +++ linux-2.6.28/net/sunrpc/clnt.c
> > @@ -128,6 +128,7 @@ static struct rpc_clnt * rpc_new_client(
> >  	struct rpc_version	*version;
> >  	struct rpc_clnt		*clnt = NULL;
> >  	struct rpc_auth		*auth;
> > +	struct new_utsname	*uts_ns = init_utsname();
> >  	int err;
> >  	size_t len;
> > 
> > @@ -213,10 +214,12 @@ static struct rpc_clnt * rpc_new_client(
> >  	}
> > 
> >  	/* save the nodename */
> > -	clnt->cl_nodelen = strlen(init_utsname()->nodename);
> > +	if (current->nsproxy != NULL)
> > +		uts_ns = utsname();
> > +	clnt->cl_nodelen = strlen(uts_ns->nodename);
> >  	if (clnt->cl_nodelen > UNX_MAXNODENAME)
> >  		clnt->cl_nodelen = UNX_MAXNODENAME;
> > -	memcpy(clnt->cl_nodename, init_utsname()->nodename, clnt->cl_nodelen);
> > +	memcpy(clnt->cl_nodename, uts_ns->nodename, clnt->cl_nodelen);
> >  	rpc_register_client(clnt);
> >  	return clnt;
> > 
> > 
> > -- 
> > _______________________________________________
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