linux-kernel - Re: [uml-devel] Issues with a rather unusual configured NFS server

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Message-ID: <20130830142503.GA31129@pad.fieldses.org>
Date:	Fri, 30 Aug 2013 10:25:03 -0400
From:	"J. Bruce Fields" <bfields@...hat.com>
To:	Toralf Förster <toralf.foerster@....de>
Cc:	"J. Bruce Fields" <bfields@...ldses.org>,
	richard -rw- weinberger <richard.weinberger@...il.com>,
	Linux NFS mailing list <linux-nfs@...r.kernel.org>,
	"user-mode-linux-devel@...ts.sourceforge.net" 
	<user-mode-linux-devel@...ts.sourceforge.net>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Jan Kara <jack@...e.cz>, linux-ext4@...r.kernel.org
Subject: Re: [uml-devel] Issues with a rather unusual configured NFS server

On Fri, Aug 30, 2013 at 04:10:42PM +0200, Toralf Förster wrote:
> On 08/29/2013 03:30 PM, J. Bruce Fields wrote:
> > On Thu, Aug 29, 2013 at 11:57:45AM +0200, richard -rw- weinberger wrote:
> >> On Wed, Aug 28, 2013 at 7:21 PM, Toralf Förster <toralf.foerster@....de> wrote:
> >>> On 08/27/2013 08:06 PM, J. Bruce Fields wrote:
> >>>> On Tue, Aug 13, 2013 at 05:53:14PM -0400, bfields wrote:
> >>>>> On Mon, Aug 12, 2013 at 04:36:40PM +0200, Jan Kara wrote:
> >>>>>> On Sun 11-08-13 11:48:49, Toralf Förster wrote:
> >>>>>>> so that the server either crashes (if it is a user mode linux image) or at least its reboot functionality got broken
> >>>>>>> - if the NFS server is hammered with scary NFS calls using a fuzzy tool running at a remote NFS client under a non-privileged user id.
> >>>>>>>
> >>>>>>> It can re reproduced, if
> >>>>>>>    - the NFS share is an EXT3 or EXT4 directory
> >>>>>>>    - and it is created at file located at tempfs and mounted via loop device
> >>>>>>>    - and the NFS server is forced to umount the NFS share
> >>>>>>>    - and the server forced to restart the NSF service afterwards
> >>>>>>>    - and trinity is used
> >>>>>>>
> >>>>>>> I could find a scenario for an automated bisect. 2 times it brought this commit
> >>>>>>> commit 68a3396178e6688ad7367202cdf0af8ed03c8727
> >>>>>>> Author: J. Bruce Fields <bfields@...hat.com>
> >>>>>>> Date:   Thu Mar 21 11:21:50 2013 -0400
> >>>>>>>
> >>>>>>>     nfsd4: shut down more of delegation earlier
> >>>>>
> >>>>> Thanks for the report.  I think I see the problem--after this commit
> >>>>> nfs4_set_delegation() failures result in nfs4_put_delegation being
> >>>>> called, but nfs4_put_delegation doesn't free the nfs4_file that has
> >>>>> already been set by alloc_init_deleg().
> >>>>>
> >>>>> Let me think about how to fix that....
> >>>>
> >>>> Sorry for the slow response--can you check whether this fixes the
> >>>> problem?
> >>>>
> >>> Yes.
> >>>
> >>> With the attached patch the problem can't be reproduced any longer with
> >>> the prepared test case and current git kernels.
> >>
> >> BTW: Is nobody else fuzz testing NFS?
> > 
> > I don't know.  Toralf's reports are the only ones I recall off the top
> > of my head, but I may have forgotten others.
> > 
> 
> well, 7255e71 and 3c50ba8 I'd say.

I don't know any 3c50ba8.  0c7c3e67 "nfsd4: don't close read-write opens
too soon" and 64a817cf "nfsd4: reject "negative" acl lengths" are two
other serious bugs found by your testing.  I don't recall fuzz testing
results from anyone else, but as I say I may have forgotten.

--b.
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