Hi Pat,

thanks for the quick reply!  I just created a bugzilla account.

The best I can provide quickly uses the cvmfs file system, which is not
in the standard repositories but it is a normal fuse module.

On the NFS server side:
  o) Install cvmfs:
yum install
https://ecsft.cern.ch/dist/cvmfs/cvmfs-release/cvmfs-release-2-4.el6.noarch.rpm
yum install cvmfs

  o) Configure and mount cvmfs
echo 'CVMFS_HTTP_PROXY=DIRECT' > /etc/cvmfs/default.local
echo 'CVMFS_NFS_SOURCE=yes' >> /etc/cvmfs/default.local
mkdir /mnt/cvmfs
mount -t cvmfs grid.cern.ch /mnt/cvmfs

  o) Export via NFS
echo '/mnt/cvmfs *(ro,fsid=1)' > /etc/exports
exportfs -ra


On the NFS client side:
mkdir /mnt/nfs
mount <SERVER>:/mnt/cvmfs /mnt/nfs
ls /mnt/nfs  # Server crashes


Let me see if I can produce something similar with a fuse module that
comes in the normal repository.

Cheers,
Jakob


On 11/11/14 15:23, Pat Riehecky wrote:
> On 11/11/2014 07:50 AM, Jakob Blomer wrote:
>> Dear Scientific Linux team,
>>
>> the latest kernel 2.6.32-504 crashes if a fuse file system is accessed
>> from within the kernel space.  As discovered by Simon, this happens for
>> instance when a fuse file system is re-exported via NFS.  When it
>> happens, the stack trace starts with
>>
>> BUG: unable to handle kernel NULL pointer dereference at 0000000000000030
>> IP: [<ffffffffa0202260>] fuse_dentry_revalidate+0xf0/0x400 [fuse]
>>
>>
>> The behavior was not present with the previous kernel 2.6.32-431.29.2.
>> Besides security patches, the latest kernel seems to also backport new
>> fuse features which triggers the problem.  As a workaround, we managed
>> to avoid the problem with a small kernel patch [1].
>>
>> Could you report the problem back to Redhat?  If necessary, I can
>> provide detailed steps how to reproduce it.
>>
>> Cheers,
>> Jakob
>>
>>
>> [1]
>> https://raw.githubusercontent.com/cvmfs/aufs2-standalone/aufs2.1-32-rhel6.6/rhel6.6-fuse.patch
>>
> 
> If we can get some more detailed replication steps it should help get
> the issue clearly explained to upstream.
> 
> Do you have a bugzilla account?
> 
> Pat
>