The only user-visible symptom of the issue is a SAFE panic.
A code deficiency in Dell EMC Unity OE version 5.0.5 was discovered which causes the first byte following a Netlogon authentication message structure to be overwritten. Usually, the next byte is unused because the structure is contained within a larger fixed memory allocation (either 64 or 128 bytes). However, if the structure consumes exactly 64 bytes, then the next byte would belong to another memory allocation, which would cause an SP panic.
The Netlogon authentication message structure is variable, and is made up of a combination of domain NETBIOS name, server NETBIOS name, and domain DNS name. In order to experience the issue, the variable section of the message structure must equal 38 bytes. The variable parts of the Netlogon structure are:
Domain NETBIOS Name + 2 x NETBIOS name + DNS domain name
Example:
To find the names we must reference, from the CLI, run the command svc_storagecheck --cifs --limitpoll. In the output, look for the line that contains "CIFS Server."
1609358938: SMB: 6: CIFS Server NETBIOS123[MYDOM] RC=6 (local users supported)
1609358938: SMB: 6: Full computer name=netbios123.mydomain1.com realm=MYDOMAIN1.COM
1609358938: SMB: 6: Comment='EMC-SNAS:T8.0.1.112'
1609358938: SMB: 6: if=10_VIRT12345Z0123 l=1.1.1.1 b=1.1.1.255 mac=0:X:XX:XX:XX:30
1609358938: SMB: 6: FQDN=netbios123.mydomain1.com (Updated to DNS)
From the output above, notice that the Domain NETBIOS name is MYDOM, the CIFS Server NETBIOS name is NETBIOS123, and the DNS domain name is mydomain1.com. When we do the math:
MYDOM (5) + 2 x NETBIOS123 (10 x 2) + mydomain1.com (13) = 38
This combination of Domain NETBIOS name, machine NETBIOS name, and DNS domain name would trigger the issue.
Fix
Install Unity OE version 5.0.6 to add Secure RPC functionality. For instructions on how to upgrade Dell EMC Unity OE code, follow KB article 22755:
Dell EMC Unity: How to Upgrade Dell EMC Unity OE code, (User Correctable).
Workaround
If you determine this issue may occur, or this issue has already occurred in your environment, change the length of the affected CIFS server name (either add characters or remove characters). This will cause the length of the Netlogon authentication message to not fall on exactly 64 bytes, and will preclude a panic.
Important: After the change of the Netbios name of the NAS server, you must reboot the SPs one by one to exclude the possibility of existing memory corruption before the change is made.