nova/releasenotes/notes/bug-1664931-refine-validate-image-rebuild-6d730042438eec10.yaml
Dan Smith f7c688b8ef Refined fix for validating image on rebuild
This aims to fix the issue described in bug 1664931 where a rebuild
fails to validate the existing host with the scheduler when a new
image is provided. The previous attempt to do this could cause rebuilds
to fail unnecessarily because we ran _all_ of the filters during a
rebuild, which could cause usage/resource filters to prevent an otherwise
valid rebuild from succeeding.

This aims to classify filters as useful for rebuild or not, and only apply
the former during a rebuild scheduler check. We do this by using an internal
scheduler hint, indicating our intent. This should (a) filter out
all hosts other than the one we're running on and (b) be detectable by
the filtering infrastructure as an internally-generated scheduling request
in order to trigger the correct filtering behavior.

Closes-Bug: #1664931
Change-Id: I1a46ef1503be2febcd20f4594f44344d05525446
2017-11-27 15:52:45 -05:00

21 lines
1.1 KiB
YAML

---
fixes:
- |
The fix for `OSSA-2017-005`_ (CVE-2017-16239) was too far-reaching in that
rebuilds can now fail based on scheduling filters that should not apply
to rebuild. For example, a rebuild of an instance on a disabled compute
host could fail whereas it would not before the fix for CVE-2017-16239.
Similarly, rebuilding an instance on a host that is at capacity for vcpu,
memory or disk could fail since the scheduler filters would treat it as a
new build request even though the rebuild is not claiming *new* resources.
Therefore this release contains a fix for those regressions in scheduling
behavior on rebuild while maintaining the original fix for CVE-2017-16239.
.. note:: The fix relies on a ``RUN_ON_REBUILD`` variable which is checked
for all scheduler filters during a rebuild. The reasoning behind
the value for that variable depends on each filter. If you have
out-of-tree scheduler filters, you will likely need to assess
whether or not they need to override the default value (False)
for the new variable.