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

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Message-ID: <1302816095.24028.87.camel@lade.trondhjem.org>
Date:	Thu, 14 Apr 2011 17:21:35 -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 Thu, 2011-04-14 at 22:37 +0200, Jiri Slaby wrote:
> On 04/13/2011 10:42 PM, Bryan Schumaker wrote:
> > On 04/12/2011 02:52 PM, Jiri Slaby wrote:
> >> On 04/12/2011 08:43 PM, Bryan Schumaker wrote:
> >>> On 04/12/2011 02:34 PM, Jiri Slaby wrote:
> >>>> On 04/12/2011 08:31 PM, Trond Myklebust wrote:
> >>>>>> 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?
> >>>>
> >>>> I don't know, I connect to a nfs server which is not maintained by me.
> >>>> It looks like that. How can I find out?
> >>>
> >>> If you're not using gss for anything, you could try rmmod-ing rpcsec_gss_krb5 (and other rpcsec_gss_* modules).
> >>
> >> I don't have NFS in modules. It's all built-in. And this one is
> >> unconditionally selected because of CONFIG_NFS_V4.
> > 
> > Does this patch help?
> 
> Nope, it makes things even worse:
> # mount -oro,intr XXX:/yyy /mnt/c/
> <15s delay here>
> mount.nfs: access denied by server while mounting XXX:/yyy
> 
> So in nfs4_proc_get_root I do:
>   printk("%s: %d %u\n", __func__, i, flav_array[i]);
>   status = nfs4_lookup_root_sec(server, fhandle, info, flav_array[i]);
>   printk("%s: res=%d\n", __func__, status);
> and get:
> [   18.159818] nfs4_proc_get_root: 0 1
> [   18.214872] nfs4_proc_get_root: res=-1
> [   18.214875] nfs4_proc_get_root: 1 0
> [   18.254636] nfs4_proc_get_root: res=-1
> [   18.254639] nfs4_proc_get_root: 2 390003
> [   33.252174] RPC: AUTH_GSS upcall timed out.
> [   33.252177] Please check user daemon is running.
> [   33.252192] nfs4_proc_get_root: res=-13
> 
> If I revert that back and do the same:
> [   28.275569] nfs4_proc_get_root: 0 1
> [   28.296545] nfs4_proc_get_root: res=-1
> [   28.296548] nfs4_proc_get_root: 1 390003
> [   43.296107] RPC: AUTH_GSS upcall timed out.
> [   43.296108] Please check user daemon is running.
> [   43.296121] nfs4_proc_get_root: res=-13
> [   43.296122] nfs4_proc_get_root: 2 0
> [   43.318201] nfs4_proc_get_root: res=-1
> 
> I.e. all methods fail. And what matters is the last retval. From NULL it
> is EPERM, from GSS it is EACCESS. For EPERM, mount(8) falls back to
> nfs3, for EACCESS it dies terrible death.

OK. That's good information. Thanks for testing!

I'm still curious as to why that NFS server is refusing all NFSv4 mounts
with NFS4ERR_WRONGSEC. Unless NFSv4 really is configured only to export
the root filesystem with RPCSEC_GSS, then that definitely sounds like a
bug...

Cheers
  Trond
-- 
Trond Myklebust
Linux NFS client maintainer

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

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