[BUG] `stdin` redirection from Windows to Linux not working in 6.18 kernel

[Nevuly]

Windows Version

Windows 11 25H2 (26200.8117)

WSL Version

2.6.3.0

Are you using WSL 1 or WSL 2?

• WSL 2
• WSL 1

Kernel Version

6.18.20.1

Distro Version

Ubuntu 22.04

Other Software

N/A

Repro Steps

1. Execute WSL2
2. From windows, run echoi echo hi | wsl -u root sh
3. Note that no output appears, and the return code from wsl is "1", indicating an error.

Expected Behavior

It should return hi.

C:\Users\User>echo echo hi |  wsl -u root sh
hi

C:\Users\User>

Actual Behavior

Instead of returning hi, it returns an empty string, and when checking the %ERRORLEVEL%, it returns 1.

C:\Users\User>echo echo hi |  wsl -u root sh

C:\Users\User>echo %ERRORLEVEL%
1

For more detailed information, please refer to the link below:
Nevuly/WSL2-Rolling-Kernel-Issue#42

I applied workaround patch in my custom kernel, and stdin redirection work correctly again.
Nevuly/WSL2-Linux-Kernel-Rolling@38b1178

This issue has been occurring since the commit linked below was applied:
Nevuly/WSL2-Linux-Kernel-Rolling@f0c5827

Additionally, there is a note mentioning that a rare interoperability issue between Windows and WSL2 can occur after applying the temporary patch. I am attaching this information as well.
Locietta/xanmod-kernel-WSL2#155

Diagnostic Logs

N/A - You can check WSL side logs in detailed information link.

cc @chessturo
This issue is present in all kernels starting from version 6.17 up to the latest.

[github-actions]

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[Nevuly]

This is the WSL debug console log after running echo echo hi | wsl -u root sh

[    9.155031] WSL (116) ERROR: CheckConnection: getaddrinfo() failed: -5
[   13.893139] WSL (419 - Relay(420)) ERROR: InitCreateProcessUtilityVm:1793: read failed 12
[   14.154200] WSL (2 - Interop) ERROR: SendMessage:131: Failed to write message LxMessageResultBool. Channel: InteropServer

Additionally, a Wsl/Service/E_UNEXPECTED error occurs on Windows.

C:\Users\User>echo echo hi |  wsl -u root sh

C:\Users\User>echo echo hi |  wsl -u root sh
오류입니다.
오류 코드: Wsl/Service/E_UNEXPECTED

C:\Users\User>

[chessturo]

Hi, thanks for the report. I believe this will be fixed in 6.18.20.2, which I'm hoping to have pushed to WSL2-Linux-Kernel by the end of the week. I'll be sure to test echo echo hi | wsl -u root sh on my machine, and I'll also ping you on this thread once it's out to confirm things are also resolved on your end.

[benhillis]

Hi, thanks for the report. I believe this will be fixed in 6.18.20.2, which I'm hoping to have pushed to WSL2-Linux-Kernel by the end of the week. I'll be sure to test echo echo hi | wsl -u root sh on my machine, and I'll also ping you on this thread once it's out to confirm things are also resolved on your end.

I think it's pretty likely this is the same hvsocket issue we identified since that's what we use for to relay stdin / stdout.

[Nevuly]

Hi, thanks for the report. I believe this will be fixed in 6.18.20.2, which I'm hoping to have pushed to WSL2-Linux-Kernel by the end of the week. I'll be sure to test echo echo hi | wsl -u root sh on my machine, and I'll also ping you on this thread once it's out to confirm things are also resolved on your end.

I think it's pretty likely this is the same hvsocket issue we identified since that's what we use for to relay stdin / stdout.

Yes, it seems it is indeed an issue related to hvsock. Looking at the commit I attached that caused the issue, it was changed to accurately return the number of readable bytes. However, in the case of stdin / stdout, since there is no byte count, it returns -EIO, which causes it to stop working.

[Nevuly]

I checked the 6.18.20.3 kernel today and confirmed that the issue has been resolved.

cc @chessturo