Noble /boot mount failures

[Matthew Ruffell]

Hi Krister,

Thanks again for tracking down another of these super subtle race
conditions.

I have prepared debdiffs for noble, oracular and plucky. We just need to
land
the change in plucky first before we can SRU to noble.

I have asked the Foundations Team to sponsor, hopefully the debdiff is up to
their expectations.

Thanks,
Matthew

On Thu, 5 Dec 2024 at 07:24, Krister Johansen <kjlx at templeofstupid.com>
wrote:

> Hi,
> I wanted to raise awareness about a bug that my team has been running
> into on Noble.  I logged a launchpad bug here with the details:
>
> https://bugs.launchpad.net/ubuntu/+source/util-linux/+bug/2090972
>
> The short explanation is that libblkid in util-linux can misread the
> ext4 superblock checksum and incorrectly decide that it doesn't match.
> If it's systemd-udevd using libblkid to do this, then that can result in
> udev removing devlinks that it thinks don't exist any longer, even
> though the device is still present.  (E.g. if libblkid doesn't find a
> filesystem, then it doesn't return the label property, and a label
> property disappearing can result in udev removing that devlink).
>
> The mount of /boot fails, because it's trying to use a
> /dev/disk/by-label path, and that path sometimes disappears because of
> the bug.  This subsequently results in packaging operations and anything
> else that interacts with /boot failing.  (Usually update-grub related).
>
> We've also seen the root disk have this problem, though the failure
> there was more subtle.  The device mounted, but a subsequent mkinitramfs
> failed during a kernel package install, because of missing
> /dev/disk/by-label links.
>
> I've fixed the bug in libblkid and gotten the fix merged upstream.
> We've also patched this locally in our own version of util-linux.  I've
> attached a patch to the bug report which is the version of the fix we
> used against the Noble packages.  We haven't seen the problem reproduce
> since rolling this out.
>
> The underlying problem affects util-linux >= 2.39.  Would it be possible
> for somebody to pull this patch into the affected Ubuntu util-linux
> versions?
>
> Thanks,
>
> -K
>
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