Hi Ben, Thanks for trying the test kernel out. Its great to hear that your analysis was correct, and it was "x86: Increase brk randomness entropy for 64-bit systems" causing the issues.
I am still deciding what to do. You see, I came across this mailing list thread: https://lore.kernel.org/all/202411210628.ECF1B494D7@keescook/T/ where Kees asked to revert from stable tree, but in the end, Greg K-H decided that it should stay in the kernel and QEMU should be fixed instead. Let me establish the blast radius of this first, and figure out what needs fixing and what doesn't. But I think we should follow Debian and fix QEMU. I will write back soon. Thanks, Matthew ** Also affects: qemu (Ubuntu) Importance: Undecided Status: New ** Changed in: linux-aws (Ubuntu) Status: New => Won't Fix ** Also affects: qemu (Ubuntu Focal) Importance: Undecided Status: New ** Also affects: linux-aws (Ubuntu Focal) Importance: Undecided Status: New ** Also affects: qemu (Ubuntu Jammy) Importance: Undecided Status: New ** Also affects: linux-aws (Ubuntu Jammy) Importance: Undecided Status: New ** No longer affects: linux-aws (Ubuntu Jammy) ** No longer affects: linux-aws (Ubuntu Focal) ** No longer affects: linux-aws (Ubuntu) ** No longer affects: qemu (Ubuntu Jammy) ** No longer affects: qemu (Ubuntu Focal) -- 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 qemu 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/qemu/+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
