Kubuntu UBSAN array-index-out-of-bounds error bricked my system (update to kernel 6.5)

[sodgian]

For how long will I receive security updates in Kubuntu 22.04 LTS with kernel version 6.2?

[claydoh]

6.2 has already been superceded by 6.5.
6.2 is the kernel from Lunar 23.04. which reached EOL at the end of January.

For LTS releases, the original kernel is supported for the full 5 year support cycle - 5.15 for 22.04
Newer kernels via the HWE don't have long support cycles, once a new major version comes out. The same lifespan as the Ubuntu releases they came from.
https://ubuntu.com/kernel/lifecycle
As 6.2 has already reached eol, and shouldn't see any more security patches.

Once the next HWE kernel update happens to 22.04 (to be the upcoming 6.8 expected in 24.04LTS), that will have support for the remainder of Jammy's life cycle, and beyond.

[sodgian]

Do you think that is a good idea to wait until kernel 6.8 is released and install it using Mainline kernels (now that I have removed linux-generic, linux-generic-hwe-22.04, linux-image, linux-header,... and will not see any security nor kernel updates)?:

[claydoh]

Up to you. Mainline (vanilla) kernel builds have zero security support, just new versions, which may or may not fix a particular hole.
Any kernel via Mainline has no real relation to what will be in Ubuntu releases, these are just basic, unmodified kernel builds as opposed to ones that have been built specifically for distro release to fit into the systems well and have some hardware support baked in properly.
They are good for testing general hardware support, so there is no reason to wait for 6.8, try some others and see if other versions may work.

Also, removing the HWE stack of course removes the chance that that you will get a fixed 6.5.0, or a grub kernel config edit is needed for your specific hardware.

[sodgian]

OK, this solved the issue that I originally had with kernel 6.5 (Kubuntu failed to start):

sudo apt remove --purge linux-modules-6.5.0-14-generic linux-image-6.5.0-14-generic linux-headers-6.5.0-14-generic linux-modules-extra-6.5.0-14-generic

sudo apt remove --purge linux-image-generic-hwe-22.04 linux-headers-generic-hwe-22.04 linux-generic-hwe-22.04

sudo apt update

Should I execute these commands to enable again kernel updates (without installing kernel 6.5)?:

sudo apt install linux-image-generic-hwe-22.04 linux-headers-generic-hwe-22.04 linux-generic-hwe-22.04

sudo apt update

Thanks in advance

[Schwarzer Kater]

[…]
Should I execute these commands to enable again kernel updates (without installing kernel 6.5)?:

sudo apt install linux-image-generic-hwe-22.04 linux-headers-generic-hwe-22.04 linux-generic-hwe-22.04

sudo apt update

Thanks in advance

You can add the --dry-run flag to simulate the installation without actually installing anything - see what will happen and decide for yourself:
sudo apt install --dry-run linux-image-generic-hwe-22.04 linux-headers-generic-hwe-22.04 linux-generic-hwe-22.04

If I understood you correctly you want to use the 5.15 LTS or 6.2.x kernel until the hwe kernel for 22.04 is at least version 6.6.x …

[claydoh]

Should I execute these commands to enable again kernel updates (without installing kernel 6.5)?:

No, this WILL bring back the 6.5. But it also won't remove a 5.15 if you still happen to have that.
And , since the 6.2 was the previous HWE, it will eventually want to get removed as the 6.5 is updated - apt wants to keep three kernels installed before auto-removing.

if you want to stick to the original (GA) kernel 5.15, then :
sudo apt install --install-recommends linux-generic


Extra tip:
Update first, then install packages, just for a good habit:
sudo apt update && sudo apt install --install-recommends linux-generic-hwe-22.04

To keep the specific 6.2 kernel from being auto-removed, then you will want to mark it as manually installed:

sudo apt mark manual linux-image-6.2.0-39-generic
Or whatever specific one you are using


if you do install the HWE kernel, you still will need to select the desired kernel version in Grub, else modify that configuration to use a specific entry as the main boot option.

[sodgian]

This command...:

sudo apt update && sudo apt install --install-recommends linux-generic-hwe-22.04

...reinstalled kernel 6.5!

Fortunately, I am using another NVIDIA graphics card with a different NVIDIA driver version (535) and now all seems to be working fine.

So, on my system, there was definitely some issue with my old NVIDIA graphics card, NVIDIA driver version 390 and kernel 6.5.

Now I have removed all the previous kernels to free up space:

[Schwarzer Kater]

This command...:

sudo apt update && sudo apt install --install-recommends linux-generic-hwe-22.04

...reinstalled kernel 6.5!

[…]

And that's exactly why I suggested to use the --dry-run flag with apt install - so you could see that it would reinstall it…

But I am glad that it works now nevertheless.

[sodgian]

Ooops... I am still getting the UBSAN message while booting:



But at least now the GUI starts normally (fingers crossed).

As far as I know this is a well-known issue and hopefully it will be fixed soon.

[claydoh]

But at least now the GUI starts normally

You can ignore this, it probably is just a 'leakage', as only actual errors or failures are normally seen - this doesn't show either tag, so it is informational. The hard part is that this is what is shown on the screen when you see your problems, which doesn't necessarily reflect the actual cause of a boot failure.