netdev - Re: [PATCH] NFS: Fix infinite loop in gss_create

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Date:	Tue, 12 Apr 2011 14:31:28 -0400
From:	Trond Myklebust <Trond.Myklebust@...app.com>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	Bryan Schumaker <bjschuma@...app.com>,
	Jiri Slaby <jirislaby@...il.com>, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, mm-commits@...r.kernel.org,
	ML netdev <netdev@...r.kernel.org>, linux-nfs@...r.kernel.org
Subject: Re: [PATCH] NFS: Fix infinite loop in gss_create_upcall()

On Tue, 2011-04-12 at 20:05 +0200, Jiri Slaby wrote:
> On 04/12/2011 07:41 PM, Bryan Schumaker wrote:
> > On 04/11/2011 05:08 PM, Jiri Slaby wrote:
> >>
> >> Sorry for an extra message. I've just found out that there appears
> >> messages in dmesg:
> >> [   58.656048] RPC: AUTH_GSS upcall timed out.
> >> [   58.656050] Please check user daemon is running.
> >> [   88.656065] RPC: AUTH_GSS upcall timed out.
> >> [   88.656068] Please check user daemon is running.
> >> [  118.656077] RPC: AUTH_GSS upcall timed out.
> >> [  118.656080] Please check user daemon is running.
> >> [  148.656049] RPC: AUTH_GSS upcall timed out.
> >> [  148.656052] Please check user daemon is running.
> >> [  178.656046] RPC: AUTH_GSS upcall timed out.
> >> [  178.656049] Please check user daemon is running.
> >>
> >>
> >> I instrumented the code and it's stuck with trying RPC_AUTH_GSS_KRB5.
> >>
> >> I don't use GSS at all.
> >>
> >> regards,
> > 
> > Does this patch help?
> > 
> > - Bryan
> > 
> > 
> > 
> > There can be an infinite loop if gss_create_upcall() is called without
> > the userspace program running.  To prevent this, we return -EACCES if
> > we notice that pipe_version hasn't changed (indicating that the pipe
> > has not been opened).
> 
> Yes, it fixes the problem. But it waits 15s before it times out. This is
> inacceptable for automounted NFS dirs.

I'm still confused as to why you are hitting it at all. In the normal
autonegotiation case, the client should be trying to use AUTH_SYS first
and then trying rpcsec_gss if and only if that fails.

Are you really exporting a filesystem using AUTH_NULL as the only
supported flavour?

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@...app.com
www.netapp.com

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