Re: Umask ignored when mounting NFSv4.2 share of an exported Filesystem with noacl (was: Re: Bug#962254: NFS(v4) broken at 4.19.118-2)

[Salvatore Bonaccorso <carnil@debian.org>]

Hi Bruce,

On Mon, Jun 15, 2020 at 10:50:35AM -0400, J. Bruce Fields wrote:
> On Sat, Jun 13, 2020 at 11:45:27AM -0700, Elliott Mitchell wrote:
> > I disagree with this assessment.  All of the reporters have been using
> > ZFS, but this could indicate an absence of testers using other
> > filesystems.  We need someone with a NFS server which has a 4.15+ kernel
> > and uses a different filesystem which supports ACLs.
> 
> Honestly I don't think I currently have a regression test for this so
> it's possible I could have missed something upstream.  I haven't seen
> any reports, though....
> 
> ZFS's ACL implementation is very different from any in-tree
> filesystem's, and given limited time, a filesystem with no prospect of
> going upstream isn't going to get much attention, so, yes, I'd need to
> see a reproducer on xfs or ext4 or something.

I think the following is reproducible on a ext4 exported share (with
underlying filesystem mounted with noacl to mimic the suspect from the
reporter). I tested the same with an older kernel from Debian stretch
(running 4.9.210-1+deb9u1) but this does not show the same behaviour.

The current test system is running 5.6.14-2 Debian kernel (so 5.6.14).

1/ Create an ext4 filesystem:

# mkfs.ext4 /dev/vdb1

2/ Mount the filesystem with noacl (to mimic the situation):

/dev/vdb1 /srv/data ext4 defaults,noacl 0 0

root@nfs-test:~# mount | grep vdb1
/dev/vdb1 on /srv/data type ext4 (rw,relatime,noacl)

3/ Export with

/srv/data 192.168.122.1/24(rw,sync,no_subtree_check,no_root_squash)

4/ Reproduce the issue

root@nfs-test:~# mount -t nfs 192.168.122.150:/srv/data /mnt
root@nfs-test:~# mkdir /mnt/foo && ls -ld /mnt/foo && rmdir /mnt/foo
drwxrwxrwx 2 root root 4096 Jun 15 20:24 /mnt/foo
root@nfs-test:~# mount | grep data
/dev/vdb1 on /srv/data type ext4 (rw,relatime,noacl)
192.168.122.150:/srv/data on /mnt type nfs4 (rw,relatime,vers=4.2,rsize=524288,wsize=524288,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,clientaddr=192.168.122.150,local_lock=none,addr=192.168.122.150)
root@nfs-test:~# umount /mnt

Looking at a wireshark captured sniff, the situation was the same as in the
previous ZFS case, in the gettattr from the client and the server does indicate
support for the new mode_umask. Then later in the CREATE operation, the client
sets the mode_umask attribute, with mode part set to '0777' and umask to '022'.
The mode replied is then as well '0777'.

Notabene: if not mounting the filesystem with noacl, then there is no
observed behaviour change here.

Regards,
Salvatore