dotnet run error Assert failure(PID 28188 [0x00006e1c], Thread: 26664 [0x6828]) in .net 9

[mammadkoma]

Description

I create a web api .net 9 project, it builds but after running dotnet run command it shows error. I don't have any problem in .net 8 on Windows 10.
The commands in .net 9 :
PS D:\TestProjects\WebApi> dotnet build
Restore complete (0.2s)
WebApi succeeded (2.4s) → bin\Debug\net9.0\WebApi.dll

Build succeeded in 3.0s
PS D:\TestProjects\WebApi> dotnet run
Using launch settings from D:\TestProjects\WebApi\Properties\launchSettings.json...
Building...
CLR: Assert failure(PID 28188 [0x00006e1c], Thread: 26664 [0x6828]): !AreShadowStacksEnabled() || UseSpecialUserModeApc()
File: D:\a_work\1\s\src\coreclr\vm\threads.cpp:7938 Image:
D:\TestProjects\WebApi\bin\Debug\net9.0\WebApi.exe
PS D:\TestProjects\WebApi>

Reproduction Steps

create a web api in .net 9

Expected behavior

running the project

Actual behavior

getting error

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

No response

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[mangod9]

@mammadkoma this looks related to CET. Are you able to reproduce the failure on different machines? Can you try to disable CET and check if the problem persists: https://learn.microsoft.com/en-us/dotnet/core/compatibility/interop/9.0/cet-support

[mammadkoma]

It runs after adding this line to the .csproj file :
<CETCompat>false</CETCompat>

So why should I add this line for .net 9 ?

[mangod9]

are you able to share a repro? Is this a simple webapi project created with dotnet new webapi ?

[mammadkoma]

Yes I created by dotnet new webapi command. It has this problem in other project types for example blazor webapp.

[JustArchi]

Also got user of my OSS app running into the same issue: JustArchiNET/ArchiSteamFarm#3348

Can't provide much more details on their environment, but the app definitely doesn't start now after .NET 9 upgrade.

CLR: Assert failure(PID 10336 [0x00002860], Thread: 9268 [0x2434]): !AreShadowStacksEnabled() || UseSpecialUserModeApc()
File: D:\a_work\1\s\src\coreclr\vm\threads.cpp:7938 Image:
D:\program\ASF-win-x64\ArchiSteamFarm.exe

[mangod9]

@janvorli FYI. Can they provide details on the hardware they are running on. Also weird that the assert is showing up here. Any repro and/or dumps if available would be helpful to diagnose.

So why should I add this line for .net 9 ?

in .NET 9 CET compat-mode is enabled by default, so if the hardware is capable CET would be enabled. It appears there are specific cases where it isnt quite working right.

[janvorli]

This means that the Windows are out of date quite a lot and so they don't contain the fix for a bug in the kernel that prevents .NET to work with CET enabled. I believe the fix was released about a year ago.

[mangod9]

Can we possibly report a better error here? Not sure how the assert shows up on release builds?

[MichalPetryka]

Can we possibly report a better error here? Not sure how the assert shows up on release builds?

runtime/src/coreclr/vm/threads.cpp

Line 7833 in 342936c

_ASSERTE_ALL_BUILDS(!AreShadowStacksEnabled() || UseSpecialUserModeApc());

It's a release assert.

[janvorli]

Can we possibly report a better error here?

We can replace that assert by a check and failfast with a message that will make more sense.

[mangod9]

yeah a better error with some details on required windows versions would be good for better clarity.

[wwh1004]

CPU: i7 11800H
OS: Windows 10 LTSC 21H2 19044.1288 in Hyper-V VM
Repo: https://github.com/dotnet/samples/tree/main/core/extensions/OutOfProcCOM/ExeServer
Publish config: net9.0-windows+win-x64+self-contained
CLR Version: 9,0,24,52809 @Commit: 9d5a6a9

C:\Users\admin\Desktop\net9.0-windows>ExeServer.exe /regserver
CLR: Assert failure(PID 4316 [0x000010dc], Thread: 4788 [0x12b4]): !AreShadowStacksEnabled() || UseSpecialUserModeApc()
    File: D:\a\_work\1\s\src\coreclr\vm\threads.cpp:7938 Image:

[mangod9]

@wwh1004 so looks like you are running an older version of windows which doesnt support the required CET apis.

[janvorli]

@wwh1004 I've asked Windows kernel developers and they confirmed that the version of Windows you have doesn't have support for the feature .NET CET support depends on. It was added in an update in 2023. So you need to either disable CET for your app or update your Windows.

[PJB3005]

This should probably be documented on the breaking change page, as .NET is still listed as being supported on these old Windows versions, and there's no indication that CET needs to be disabled in that scenario.