samba - Jan 2025 - Different behavior when client uses "sec=none" and when provides bad user (mapped to guest)

?
HI everyone.

I've been analyzing a problem with an embedded Linux/FPGA device that in
some cases was failing to run properly when using files from a samba share.
After some time I've found it is related to Samba bug 12783 and setting
kernel oplocks on global fix the issue.

But while looking at that I have found a strange behavior I can't
understand. I have guest ok = yes on the share and map to guest = Bad User on
global.

If I mount the share with a bad user, everything works OK and I can see the
device lock on the file with smbstatus.

But if I mount the samba share with sec=none , the program will throw an error,
I think because it wasn't able to adquire a lock on the file - I don't
see a lock in smbstatus.

In both cases the connection is assigned to nobody, as configured for guest
connections. I run samba 4.20.5 on Truenas Scale 24.10 . I have attached to this
mail:

- the output of testparm -s

- the audit logs provided by Truenas when I connect with bad user and with
sec=none

- the smbstatus when connected with bad user and with sec=none

Any idea what can be happening?

Best Regards,

Carlos A. Balseiro

On Fri, 17 Jan 2025 22:32:03 +0100
Carlos Alberto Balseiro Mayi via samba <samba at lists.samba.org> wrote:
> ?
> HI everyone.
> 
> I've been analyzing a problem with an embedded Linux/FPGA device that
> in some cases was failing to run properly when using files from a
> samba share. After some time I've found it is related to Samba bug
> 12783 and setting kernel oplocks on global fix the issue. 
> 
> But while looking at that I have found a strange behavior I can't
> understand. I have guest ok = yes on the share and map to guest = Bad
> User on global.
> 
> If I mount the share with a bad user, everything works OK and I can
> see the device lock on the file with smbstatus.
> 
> But if I mount the samba share with sec=none , the program will throw
> an error, I think because it wasn't able to adquire a lock on the
> file - I don't see a lock in smbstatus.
> 
> In both cases the connection is assigned to nobody, as configured for
> guest connections. I run samba 4.20.5 on Truenas Scale 24.10 . I have
> attached to this mail:
> 
> - the output of testparm -s
> 
> - the audit logs provided by Truenas when I connect with bad user and
> with sec=none
> 
> - the smbstatus when connected with bad user and with sec=none
> 
> Any idea what can be happening?
> 
> Best Regards,
> 
> Carlos A. Balseiro
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Rowland