[Samba] Windows 10 app crashing after fileserver update from Samba 4.2 to 4.5

[Mgr. Peter Tuharsky]

Hi,

we have a network-hosted app for windows that is being executed from smb
share. The app worked well with Windows up to 7.

Now, after upgrading clients to Windows 10, the app suddenly crashes
after some 1-2 hours of use (or idle). The vendor indicates, that the
problem may relate to reading the app's DLLs.

The interesting thing is, that the problem only appears when the share
is hosted on Samba 4.5(.12) or Windows 2016 server.

We don't see the problem on Samba 4.2 or Windows 2008R2 server. However,
due to security and infrastructure reasons we don't see possibility to
keep these systems for too long.

We would like to migrate the app to Samba 4.5. I feel, that the culprit
must be some new SMB functionality that appeared both on Windows 10,
Windows 2016 and Samba 4.5, that makes the difference against the older
Windows and Samba systems. Some kind of caching, locking, or something
like that. Maybe related to SMB v3? Theoretically, the code might even
have been present in older Samba too, but may have been enabled only
later by changing some default between versions.

If I could switch the feature back to the old way in config, it may
workaround the problem. I just don't know, which one could it be. Does
anyone have a clue?