[Samba] Operation Not Supported error for GETXATTR when VFS plugin "nfs4acl_xattr" is used

[Jeremy Allison]

On Fri, Apr 06, 2018 at 09:22:17PM +0200, Ralph Böhme wrote:
> On Fri, Apr 06, 2018 at 10:27:32AM -0700, Jeremy Allison via samba wrote:
> > On Fri, Apr 06, 2018 at 01:44:50PM +0530, Akash Jain wrote:
> > > Hi All
> > > 
> > > I found there is one bug in the plugin. The name of the attribute for ACL as
> > > per strace output of nfs4_setfacl is system.nfs4_acl.
> > > The source code has defined it as
> > > #define NFS4ACL_XATTR_NAME      ( "system.nfs4acl" )
> > > 
> > > Note there is missing underscore.
> > > 
> > > After this, the EOPNOTSUPP error is not observed.
> > > 
> > > Hope this helps
> > 
> > Hmmm. This has been changed for Samba 4.8.0 and above,
> > with commit df99ac27106dededcf0a98a251e58c24b90bf6d1.
> > 
> > This would seem to be a correct fix, as it seems
> > 
> > "The "system" xattr namespace is reserved for the kernel. Any attempt to
> >     use xattrs in that namesspace will fail with EOPNOTSUPP, regardless of
> >     priveleges."
> > 
> > Can you check with 4.8.x ?
> 
> I guess that statement may not be correct, depending on which kernel subsystem
> exposes the xattr? My testing was with local filesytems, not with nfsv4
> mounts. Apparantly it works with nfs4_getfacl|nfs4_setfacl...

Ah, my guess is there's a missing check in the kernel
NFSv4 redirector somewhere. Anyway, we can't use system.XXX
namespace if it doesn't work on local filesystems on
Linux.