Score:3

Problems after installation of KB5025229/KB5025230 on Azure VM with Windows Server 2019/2022

id flag

After installation of KB5025229/KB5025230 we are getting errors in our software:

System.IO.IOException: The process cannot access the file '{file}' because it is being used by another process.

After de-installation of KB5025229/KB5025230 the problem is gone. The problem occurred on multiple Azure VM's with Windows Server 2019 and Windows Server 2022.

Software is a c# dotnetframework4.7 asp.net MVC website running on IIS. Problem occurs on writing a temp file; this file is opened and closed multiple times in a short time, each time new data is added to the file.

This file is stored on an Azure Storage Account File Share.

So it looks like another process is locking the file now, what process can this be? Maybe Defender checking the changed file? I looked into the changes in KB5025229 but could not see anything related to this.

Does anyone have any ideas on this?

Jeff Mergler avatar
in flag
You're not alone. We see the same problem and error message with a .NET 4.7 Windows Service we wrote running on a Windows Server 2019 VM at a customer site. This Windows Service is simple: it polls a folder intermittently and reads files that are dropped into it and manipulates them using XSL and passes them on to a database. This service was installed years ago and was working without problems and only broke after KB5025229 was installed. Once KB5025229 was uninstalled the service works without error. The referenced {file} in our 'System.IO.IOException' error is the log file for the service.
Jeff Mergler avatar
in flag
Do you see any additional details in the Windows Event Log when your MVC application raised the error? I've requested the Windows Event Log from my customer so I can examine it for clues. My customer also mentions that the Windows Update had something to do with Defender.
Poiter avatar
id flag
No, nothing in the Event Log. We changed our code to work around the problem, so for now we solved it and hope its the only problem with this update!
Jeff Mergler avatar
in flag
Hi @Poiter, can you elaborate on your code change? Did change anything related to System.IO ?
Poiter avatar
id flag
We were writing different 'chunks' to a 'temp' file, and each time we opened and closed this file (with Syste,IO.File.Open()). Now we open this file only once until all the 'chunks' are written...
Score:0
cn flag

So it looks like an other process is locking the file now, what process can this be?

You need to enable auditing at both the system level and on the file to record this information in the event log. You can also use tools such as SysInternals ProcMon to identify file access in a more hyper-accurate manner. Given that the symptom is easily reproducible in a short period of time, it should not take long to identify the offending process.

https://learn.microsoft.com/en-us/sysinternals/downloads/procmon

Poiter avatar
id flag
For now, we solved the problem by changing our code, so we are not looking further into the cause. But thanks for the suggestion!
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