Kernel dns_resolver not working

[jabbera]

Note: This is NOT a dupe of: #8365

Version

Microsoft Windows [Version 10.0.22621.1105]

WSL Version

• WSL 2
• WSL 1

Kernel Version

CUSTOM 5.15.83.1-microsoft-standard-WSL2

Distro Version

22.04.01

Other Software

No response

Repro Steps

Compile kernel with DFS config options and mount a DFS share. (or try to mount and NFS 4.1 share with a redirect I think)

CONFIG_CIFS_UPCALL=y
CONFIG_CIFS_DFS_UPCALL=y
CONFIG_CIFS_SWN_UPCALL=y

Mount:

[ 95.460468] kernel: [mount.] ==> dns_query((null),MARPRDDFS001.top.tld,20,(null))
[ 95.460473] kernel: [mount.] call request_key(,MARPRDDFS001.top.tld,)
[ 95.463970] kernel: do_filp_open returnuing error: /sbin/request-key
[ 95.463972] kernel: do_filp_open returnuing error: -2
[ 95.464092] kernel: [mount.] <== dns_query() = -2

Expected Behavior

request-key upcall should work

Actual Behavior

request-key upcall fails. I dug into this until my brain hurt and for some reason the linked line below is returning -2 in WSL but does not on standard ubuntu:

https://github.com/microsoft/WSL2-Linux-Kernel/blob/292031a0f1af813fddf924151f5cccfa2f6f4642/fs/exec.c#L918

I can tell request-key isn't being called because I replaced it with a custom binary that just sleeps and touches a marker file.

Diagnostic Logs

No response

[jabbera]

Side question: Is there a way to actually use a debugger on a custom kernel? I did all of this via printk and it was painful.

[jaltman]

The root cause of this issue is the lack of keyutils being installed in the CBL-Mariner base image. As a result, the kernel's attempt to execute /bin/request-key to perform the dns resolution upcall fails.

[jabbera]

@jaltman is the mariner image the vm image that runs the wsl container instances?

[jaltman]

@jaltman is the mariner image the vm image that runs the wsl container instances?

Yes