A new kernel, 2.6.24-17, has been released for Ubuntu 8.04 (Hardy Heron) in the hardy-updates repository. This kernel may fix at least 1 xen bug (bug 218126, bug 204010) which I’m anxious to test. I’ve held off upgrading any Xen user domains until these were resolved. I think it would be a good time to at least test an upgrade, and since virtualization makes it easy to rollback I think a test is in order. I also noticed that Ubuntu 7.10 got some new kernel modules in the gutsy-updates repository. Not sure what the changes are but it’s something to be aware of.

Yes Linus Torvalds announced the release of the 2.6.25 kernel today. I’ve been trying to confirm whether the TASK_KILLABLE patches have been included. It has been mentioned in the comments of the LWM article announcing the 2.6.25 release but the Kernel Newbies 2.6.25 page only lists:

“softlockup: automatically detect hung TASK_UNINTERRUPTIBLE tasks”

Honestly after reading about the other big changes this is the one that has the most effect on my work. The addition of LatencyTop support should help improve desktops running Linux and I look forward to playing with it. But most of the other changes do not address issues that I am experiencing while the TASK_KILLABLE patches most certainly do. I will have to do more research on the state of these patches; perhaps they don’t seem like a big deal to other people but I’m surprised that such an important change wouldn’t be mentioned.

I just did some reading on unkillable processes. I've seen this happen a few times before and wondered what caused it. I experienced it again today when using KVM. Apparently when processes go into the "D" state they cannot be killed because they are usually waiting for some IO to complete. I have not found any way to fix these processes while a system is running though I continue to investigate. I did find that the 2.6.25 Linux kernel will add a new TASK_KILLABLE state to help alleviate this problem. Hopefully software including KVM will be quickly updated to take advantage of this new state which functions just like TASK_UNINTERRUPTIBLE but allows the process to be killed.

New kernel releases have been released by both the Ubuntu and Debian teams. Both address CVE-2008-0600 which could allow an attacker to escalate their privileges. The Debian vserver kernels have also been updated to address CVE-2008-0163 which allows users in one vserver to access information in another. For Ubuntu this comes just a week after the last Linux kernel security update.

• DSA-1494-1 linux-2.6 — missing access checks
• USN-577-1: Linux kernel vulnerability
• USN-574-1: Linux kernel vulnerabilities
• Patching CVE-2008-0600, Local Root Exploit

Time to update those kernels. Here are the details:

• Debian: DSA-1436-1 linux-2.6 — several vulnerabilities
• Ubuntu: USN-558-1: Linux kernel vulnerabilities