linux-kernel - Re: NFS regression in 2.6.37.1 (current stable)

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Date:	Thu, 10 Mar 2011 14:39:25 -0500
From:	Trond Myklebust <Trond.Myklebust@...app.com>
To:	Dr Andrew John Hughes <ahughes@...hat.com>
Cc:	linux-kernel@...r.kernel.org, stable@...nel.org, mkl@...gutronix.de
Subject: Re: NFS regression in 2.6.37.1 (current stable)

On Thu, 2011-03-10 at 18:53 +0000, Dr Andrew John Hughes wrote: 
> [Please CC me on responses as I'm not subscribed]
> 
> Hi,
> 
> I seem to have uncovered a regression in the NFS code between 2.6.37 and 2.6.37.1
> caused by this changeset:
> 
> commit 55ea499d60aefa3d03a77fc8590c26b5881faa92
> Author: Trond Myklebust <Trond.Myklebust@...app.com>
> Date:   Sat Jan 8 17:45:38 2011 -0500
> NFS: Don't use vm_map_ram() in readdir
> http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.37.y.git;a=commit;h=6650239a4b01077e80d5a4468562756d77afaa59
> 
> With this change applied, copying of files between NFS and non-NFS
> mounts seems to be broken.  The easiest way I've found to replicate
> this myself is to use a VCS to do a clone of a tree on a NFS mount to
> a directory on a non-NFS mount.  I used Mercurial, as I had Mercurial
> trees to hand from work on IcedTea, but I assume doing it with a git
> tree such as the linux tree would also work.  The idea is to do
> something which involves copying over a bunch of directories and
> checking the result is readable.
> 
> $ hg clone $HOME/projects/openjdk/icedtea6-hg
> destination directory: icedtea6-hg
> updating to branch default
> abort:
> data/contrib/templater/hotspot/src/cpu/CPU/vm/bytecodeInterpreter_CPU.inline.hpp.i@...04ce16287:
> no match found!
> 
> In the above, $HOME is an NFS mount and $PWD is a local reiserfs
> partition.  I initially hit failures doing builds with source on $HOME
> and the build directory on a local reiserfs partition.  In that
> scenario, it would fail as not being able to find files that should
> have been copied over.
> 
> Reverting the changeset fixes the issue.  2.6.37.2 still has the bug.
> I haven't checked 2.6.37.3 yet but I didn't see any NFS changes in there.
> --
> Andrew :)
> 
> Free Java Software Engineer
> Red Hat, Inc. (http://www.redhat.com)

It looks to me as if you are hitting the issue that was fixed in
mainline by commit d1205f87bbb8040c1408bbd9e0a720310b2b0b9b (NFS: NFSv4
readdir loses entries). That commit was labelled as "Cc:
stable@...nel.org" but has still not made it into the 2.6.37 stable
series.

I've attached it below...

Cheers
  Trond

8<-------------------------------------------------------------------
>From d1205f87bbb8040c1408bbd9e0a720310b2b0b9b Mon Sep 17 00:00:00 2001
From: Chuck Lever <chuck.lever@...cle.com>
Date: Fri, 28 Jan 2011 12:41:05 -0500
Subject: [PATCH] NFS: NFSv4 readdir loses entries

On recent 2.6.38-rc kernels, connectathon basic test 6 fails on
NFSv4 mounts of OpenSolaris with something like:

> ./test6: readdir
> ./test6: (/mnt/klimt/matisse.test) didn't read expected 'file.12' dir
entry, pass 0
> ./test6: (/mnt/klimt/matisse.test) didn't read expected 'file.82' dir
entry, pass 0
> ./test6: (/mnt/klimt/matisse.test) didn't read expected 'file.164' dir
entry, pass 0
> ./test6: (/mnt/klimt/matisse.test) Test failed with 3 errors
> basic tests failed
> Tests failed, leaving /mnt/klimt mounted
> [cel@...isse cthon04]$

I narrowed the problem down to nfs4_decode_dirent() reporting that the
decode buffer had overflowed while decoding the entries for those
missing files.

verify_attr_len() assumes both it's pointer arguments reside on the
same page.  When these arguments point to locations on two different
pages, verify_attr_len() can report false errors.  This can happen now
that a large NFSv4 readdir result can span pages.

We have reasonably good checking in nfs4_decode_dirent() anyway, so
it should be safe to simply remove the extra checking.

At a guess, this was introduced by commit 6650239a, "NFS: Don't use
vm_map_ram() in readdir".

Cc: stable@...nel.org [2.6.37]
Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>
---
fs/nfs/nfs4xdr.c |    3 ---
1 files changed, 0 insertions(+), 3 deletions(-)

diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index 009aef9..4e2c168 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -6132,9 +6132,6 @@ int nfs4_decode_dirent(struct xdr_stream *xdr,
struct nfs_entry *entry,
if (entry->fattr->valid & NFS_ATTR_FATTR_TYPE)
entry->d_type = nfs_umode_to_dtype(entry->fattr->mode);

- if (verify_attr_len(xdr, p, len) < 0)
- goto out_overflow;
-
return 0;

out_overflow:
-- 
1.7.4



-- 
Trond Myklebust
Linux NFS client maintainer

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

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