[Bug 2044657] Re: zfs block cloning file system corruption

[Mike Ferreira]

This is my merge fo a Bug Report marked as a duplicate of this one:
https://bugs.launchpad.net/ubuntu/+source/zfs-linux/+bug/2044969

In the OpenZFS patch thread, they had said that feature at block_cloning,
because of the underlying bug, OpenZFS had said they turned that feature
off by default in 2.2.1. (They actually didn't.)

2.2.1 is in Noble Proposed. Rick S. and I have been testing it (in DEV
Noble) ever since I reported my Bug Report which recently has been
marked as a duplicate of this Bug... (Noted above)

In my tests, in version 2.2.1, that package does not turn off that
feature by default.  Noble (with zfsutils 2.2.1) creates the rpool with
feature at block_cloning=Active, as a default. I debugged the install
activity for noble during the ZFS install, and it is passing
features=defaults... That is not something that was injected i the code
of ubuntu-desktop-installer, so it still set as a default.

Just to test that, I confirmed it. If you create a new pool by defaults,
that feature gets set to enabled, unless you explicitly give it:  -o
feature at block_cloning=disabled

My previous proposal was for 2.2.1 to get pushed out of Noble Proposed
to Noble Main. But that was before we found out that was was said about
2.2.1 was wrong. Now my proposal is to build 2.2.2, move it to Noble
proposed, so Rick S. and I can test and verify it... The move it to
Noble Main.

Those go along with backporting the patch back through Focal. Yes that
feature at block_cloning uncovered the Bug, and increases the likelihood
that it occurs, but... The underlying bug in the code goes back to code
from 2012.  Focal is still in support.

Ubuntu Pro ESM is another matter, which 14.04 is still in ESM, and still
has 4 months left... But is also affected by this Bug/CVE.

We had also started a thread on this in the Noble Dev section:
https://ubuntuforums.org/showthread.php?t=2492927&p=14167819

OpenZFS did release zfs-linux 2.2.2 last week. But I do not see any zfs-
linux builds yet of that there.

Yes we know if only happens during a cp (does nto affect rsync), but the
OpenZFs patches seem to work on the ZFS end of things...

This summarizes what we had there in that bug report, into this one...

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https://bugs.launchpad.net/bugs/2044657

Title:
  zfs block cloning file system corruption

Status in linux-hwe-6.2 package in Ubuntu:
  Confirmed
Status in linux-hwe-6.5 package in Ubuntu:
  Confirmed
Status in zfs-linux package in Ubuntu:
  Confirmed

Bug description:
  OpenZFS 2.2 reportedly has a bug where block cloning might lead to
  file system corruption and data loss. This was fixed in OpenZFS 2.2.1.

  Original bug report: https://github.com/openzfs/zfs/issues/15526

  and 2.2.1 release notes:
  https://github.com/openzfs/zfs/releases/tag/zfs-2.2.1

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