samba - Nov 2020 - ERROR: pad length mismatch. Calculated 44 got 0

Hi,

Searching my samba logs for errors, I noticed the following logged 
occasionally on (all three) DCs:
> ../../librpc/rpc/dcerpc_util.c:373: ERROR: pad length mismatch. Calculated
44  got 0
Searching the samba archives, they seem to be related to DNS.

So I checked our config. We're on buster, with:
> root at dc2:~# dpkg -l | grep bind9
> ii  bind9                            1:9.11.5.P4+dfsg-5.1+deb10u2 amd64    
Internet Domain Name Server
> ii  bind9-host                       1:9.11.5.P4+dfsg-5.1+deb10u2 amd64    
DNS lookup utility (deprecated)
> ii  bind9utils                       1:9.11.5.P4+dfsg-5.1+deb10u2 amd64    
Utilities for BIND
> ii  libbind9-161:amd64               1:9.11.5.P4+dfsg-5.1+deb10u2 amd64    
BIND9 Shared Library used by BIND
(output similar for DC3 & DC4)

And:
> root at dc2:~# cat /var/lib/samba/private/named.conf
> # This DNS configuration is for BIND 9.8.0 or later with dlz_dlopen
support.
> #
> # This file should be included in your main BIND configuration file
> #
> # For example with
> # include "/var/lib/samba/private/named.conf";
> 
> #
> # This configures dynamically loadable zones (DLZ) from AD schema
> # Uncomment only single database line, depending on your BIND version
> #
> dlz "AD DNS Zone" {
>     # For BIND 9.8.x
>     # database "dlopen
/usr/lib/x86_64-linux-gnu/samba/bind9/dlz_bind9.so";
> 
>     # For BIND 9.9.x
>     # database "dlopen
/usr/lib/x86_64-linux-gnu/samba/bind9/dlz_bind9_9.so";
> 
>     # For BIND 9.10.x
>     # database "dlopen
/usr/lib/x86_64-linux-gnu/samba/bind9/dlz_bind9_10.so";
> 
>     # For BIND 9.11.x
>     database "dlopen
/usr/lib/x86_64-linux-gnu/samba/bind9/dlz_bind9_11.so";
> };
(output again similar for DC3 & DC4)

And bind seems to be running fine:
> root at dc2:~# service bind9 status
> ? bind9.service - BIND Domain Name Server
>    Loaded: loaded (/lib/systemd/system/bind9.service; enabled; vendor
preset: enabled)
>    Active: active (running) since Tue 2020-11-17 20:43:15 CET; 1 weeks 0
days ago
>      Docs: man:named(8)
>   Process: 403 ExecStart=/usr/sbin/named $OPTIONS (code=exited,
status=0/SUCCESS)
>  Main PID: 439 (named)
>     Tasks: 7 (limit: 4700)
>    Memory: 68.1M
>    CGroup: /system.slice/bind9.service
>            ??439 /usr/sbin/named -u bind
> 
> Nov 25 10:05:22 dc2 named[439]: samba_dlz: starting transaction on zone
samba.company.com
> Nov 25 10:05:22 dc2 named[439]: samba_dlz: allowing update of
signer=PATSTAT-WIN2016\$\@samba.company.com
name=patstat-win2016.samba.company.com tcpaddr=1.2.3.48 type=AAAA
key=1080-ms-7.269-b24d64f4.031a354c-c5b1-11ea-bb9b-ac1f6b
> Nov 25 10:05:22 dc2 named[439]: samba_dlz: allowing update of
signer=PATSTAT-WIN2016\$\@samba.company.com
name=patstat-win2016.samba.company.com tcpaddr=1.2.3.48 type=A
key=1080-ms-7.269-b24d64f4.031a354c-c5b1-11ea-bb9b-ac1f6b7af
> Nov 25 10:05:22 dc2 named[439]: samba_dlz: allowing update of
signer=PATSTAT-WIN2016\$\@samba.company.com
name=patstat-win2016.samba.company.com tcpaddr=1.2.3.48 type=A
key=1080-ms-7.269-b24d64f4.031a354c-c5b1-11ea-bb9b-ac1f6b7af
> Nov 25 10:05:22 dc2 named[439]: client @0x7f009011deb0 1.2.3.48#52868/key
PATSTAT-WIN2016\$\@samba.company.com: updating zone
'samba.company.com/NONE': deleting rrset at
'patstat-win2016.samba.company.com' AAAA
> Nov 25 10:05:22 dc2 named[439]: client @0x7f009011deb0 1.2.3.48#52868/key
PATSTAT-WIN2016\$\@samba.company.com: updating zone
'samba.company.com/NONE': deleting rrset at
'patstat-win2016.samba.company.com' A
> Nov 25 10:05:22 dc2 named[439]: samba_dlz: subtracted rdataset
patstat-win2016.samba.company.com 'patstat-win2016.samba.company.com.       
1200        IN        A        1.2.3.48'
> Nov 25 10:05:22 dc2 named[439]: client @0x7f009011deb0 1.2.3.48#52868/key
PATSTAT-WIN2016\$\@samba.company.com: updating zone
'samba.company.com/NONE': adding an RR at
'patstat-win2016.samba.company.com' A 1.2.3.48
> Nov 25 10:05:22 dc2 named[439]: samba_dlz: added rdataset
patstat-win2016.samba.company.com 'patstat-win2016.samba.company.com.       
1200        IN        A        1.2.3.48'
> Nov 25 10:05:22 dc2 named[439]: samba_dlz: committed transaction on zone
samba.company.com
However, over the last 24 hours, we had 41 messages "ERROR: pad length 
mismatch. Calculated 44  got 0" across all DCs.

As everything is basically running fine, I'm not too worried about them, 
but before I look into this more:

Others here observe the same?

MJ

On Wed, 2020-11-25 at 10:18 +0100, mj via samba wrote:
> Hi,
> 
> Searching my samba logs for errors, I noticed the following logged 
> occasionally on (all three) DCs:
> 
> > ../../librpc/rpc/dcerpc_util.c:373: ERROR: pad length mismatch.
> > Calculated 44  got 0
> 
> Searching the samba archives, they seem to be related to DNS.
Not DNS, but see https://bugzilla.samba.org/show_bug.cgi?id=14356

Andrew Bartlett
-- 
Andrew Bartlett                       https://samba.org/~abartlet/
Authentication Developer, Samba Team  https://samba.org
Samba Developer, Catalyst IT          
https://catalyst.net.nz/services/samba

Hi Andrew,

Wow that was a record-fast response :-)

Next time, I will not only search the mailinglist archives, but also 
bugzilla, before posting.

Thanks!

MJ


On 11/25/20 10:24 AM, Andrew Bartlett via samba wrote:
> On Wed, 2020-11-25 at 10:18 +0100, mj via samba wrote:
>> Hi,
>>
>> Searching my samba logs for errors, I noticed the following logged
>> occasionally on (all three) DCs:
>>
>>> ../../librpc/rpc/dcerpc_util.c:373: ERROR: pad length mismatch.
>>> Calculated 44  got 0
>>
>> Searching the samba archives, they seem to be related to DNS.
> 
> Not DNS, but see https://bugzilla.samba.org/show_bug.cgi?id=14356
> 
> Andrew Bartlett
>