Due to the nature of this bug (referencing previously freed memory
leading to an undefined behavior), a reliable testing procedure is
difficult to create. This bug was originally found by looking for a
cause of syncrepl failures. The reproducibility of these failures was
about 50%, enough to make syncrepl unusable, but syncrepl would
persistently fail or persistently work correctly, sometimes for long
stretches of testing iterations. While trying to set a test environment
using virtual machines, I was unable to reproduce the syncrepl failures
at all.

Because of that, in my original bug report to OpenLDAP project, I did
not describe steps to reproduce the problem, but instead provided a
debugging patch that reliably demonstrated the use-after-free issue.
This patch replaced the offending free with an assignment of a special
value to the variable that was to be freed. The value of that variable
was then examined in places where it was accessed. However, while this
approach demonstrates the bug well, it requires a rebuild of the code,
and cannot be used to test the fixed package.

I would like to add that I went the "debug-it-yourself" route precisely
because the symptoms were too unpredictable and too "mysterious" to hope
for the usual bug report to succeed (by "usual bug report" I mean
complaining about symptoms, listing steps to reproduce, etc).

To sum up, I can list steps I took during my testing, but these will be
of limited use when reproducibility is concerned. I can also provide the
debug patch with explanations. Please advise on what would be the best
course of action.

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https://bugs.launchpad.net/bugs/1557248

Title:
  OpenLDAP: Backport a fix for use-after-free in GnuTLS-related code

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