Hi Ben, I made you a test kernel with the following commit reverted:
ubuntu-jammy-aws: f5be153733b4d3dab31e3660b54660f34ff90584 commit 44c76825d6eefee9eb7ce06c38e1a6632ac7eb7d Author: Kees Cook <keesc...@chromium.org> Date: Fri Feb 16 22:25:43 2024 -0800 Subject: x86: Increase brk randomness entropy for 64-bit systems Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=44c76825d6eefee9eb7ce06c38e1a6632ac7eb7d Its not quite finished building yet, click this to make sure its finished before you go and install it: https://launchpad.net/~mruffell/+archive/ubuntu/lp2096782-test The Kernel is based on 6.8.0-1021-aws, for jammy HWE. There is no regular noble kernel here. Please note this package is NOT SUPPORTED by Canonical, and is for TESTING PURPOSES ONLY. ONLY Install in a dedicated test environment. Instructions to Install (On a jammy system): 1) sudo add-apt-repository ppa:mruffell/lp2096782-test 2) sudo apt update 3) sudo apt install linux-image-unsigned-6.8.0-1021-aws linux-modules-6.8.0-1021-aws linux-modules-extra-6.8.0-1021-aws linux-headers-6.8.0-1021-aws 4) sudo reboot 5) uname -rv Look for +TEST2096782v20250128b3 Can you try reproduce, and let me know if it looks okay? We will probably go for revert. The QEMU patch looks complex. Let me know if it works. Thanks, Matthew -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux-aws in Ubuntu. https://bugs.launchpad.net/bugs/2096782 Title: Change in 22.04 kernel causes QEMU crashes Status in linux-aws package in Ubuntu: New Bug description: I am seeing sporadic (but relatively repeatable) crashes in a g++/QEMU build environment (building on amd64, targeting arm64) when our Ubuntu kernel was updated from 6.8.0-1019.21~22.04.1 to 6.8.0-1021.23~22.04.1. While I am not 100% sure that the kernel is to blame, I do know that everything worked fine with ubuntu/images/hvm- ssd/ubuntu-jammy-22.04-${arch}-server-20241211, and it broke with ubuntu/images/hvm-ssd/ubuntu-jammy-22.04-${arch}-server-20241217. After doing some research, it seems to me that the kernel update is the most likely culprit. This kernel commit [1] (Increase brk randomness entropy for 64-bit systems, only 4 lines) was one of the many changes introduced in the 6.8.0-1020 AWS kernel update. This commit was identified as problematic by two independent developers (both working with QEMU) reporting their respective problems: [2] and [3]. Furthermore, this Linux kernel mailing list thread [4] is the suggestion/recommendation to remove this patch from "stable" kernel versions due to the risk that it breaks buggy application software. In this case QEMU is the buggy software. Supposedly, according to [5], the underlying QEMU bug was fixed in upstream QEMU in version 8.1 [6], but Ubuntu 22.04 is stuck at 6.2. I think the "Increase brk randomness entropy for 64-bit systems" patch should be reverted since it breaks another Ubuntu-supported package (QEMU 6.2). [1] - https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b0cde867b80a5e81fcbc0383e138f5845f2005ee [2] - https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1085762 [3] - https://www.mail-archive.com/debian-bugs-dist%40lists.debian.org/msg2001941.html [4] - https://www.spinics.net/lists/stable/msg792373.html [5] - https://www.mail-archive.com/debian-bugs-dist@lists.debian.org/msg2001950.html [6] - https://github.com/qemu/qemu/commit/dd55885516f42f718d0d121c59a5f7be5fdae3e6 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux-aws/+bug/2096782/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
