[Bug 2073267] Re: Virtualbox Guru meditation on VM start caused by kernel commit in v6.9-rc4

Again Guru meditation after upgrade to 6.8.0-48.48 in Jammy.

Last good kernel 6.8.0-47.

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https://bugs.launchpad.net/bugs/2073267

Title:
Virtualbox Guru meditation on VM start caused by kernel commit in
v6.9-rc4

Status in linux package in Ubuntu:
Invalid
Status in linux-hwe-6.8 package in Ubuntu:
Invalid
Status in linux-signed-hwe-5.15 package in Ubuntu:
Confirmed
Status in virtualbox package in Ubuntu:
Confirmed
Status in linux source package in Jammy:
Fix Released
Status in linux-hwe-6.8 source package in Jammy:
Fix Released
Status in linux-signed-hwe-5.15 source package in Jammy:
Invalid
Status in virtualbox source package in Jammy:
Confirmed

Bug description:
BugLink: https://bugs.launchpad.net/bugs/2073267

SRU Justification:

[Impact]

Commit "randomize_kstack: Improve entropy diffusion" changed the
kernel stack for entropy to 1KiB, limiting the thread kernel stack to
15Kib. This impacts virtualbox 6.1.50 on jammy, that is no longer
maintained upstream. The issue does not persist on version 7.0.20 due to a
code refactoring that probably resulted in less stack usage. Fixing it on
the jammy virtualbox package side is not straightfoward because the fix is
not easy to backport to 6.x and upgrading the jammy package to 7.x breaks
current users machines that run Windows, but not only.
Users need to uninstall the Guest additions drivers, migrate the
virtualbox package to 7.x, boot each VMs and install the Guest additions
drivers in each VM.

This impacts:
1. jammy:linux
2. jammy:linux-hwe-6.8
3. focal:linux-hwe-5.15

[Fix]

Revert commit "randomize_kstack: Improve entropy diffusion"

[Test Plan]

Without this fix, a VM would crash, showing with "VCPU0: Guru
Meditation -2708 (VERR_VMM_SET_JMP_ABORTED_RESUME)".
After the kernel upgrade, all VMs should run with no problem.

[Where problems could occur]
This may have an impact on security. The commit is a fix to improve the
stack entropy.

Original description:

It worked yesterday, but today I get a Guru Meditation trying to start
some of my virtual machines. This shows up in VBox.log as "VCPU0: Guru
Meditation -2708 (VERR_VMM_SET_JMP_ABORTED_RESUME)". I suspect this
may have started due to a Linux kernel upgrade I installed this
morning.

A fresh VM with no disk shows the issue. Sometimes turning off the I/O
APIC makes the issue go away, sometimes not. Turning off nested paging
sometimes lets VirtualBox make a little bit of progress w.r.t. booting
VMs, but that usually still crashes before the VM finishes starting.

This may be related to this bug reported on the VirtualBox forums:
https://forums.virtualbox.org/viewtopic.php?t=111889&sid=5cd33c0872a03b689e7e9f84d850f538

https://forums.virtualbox.org/viewtopic.php?t=111918

Ubuntu is 22.04.4 LTS, kernel is 5.15.0-116-generic, VirtualBox is
6.1.50-dfsg-1~ubuntu1.22.04.1.

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