Prevent possible double-free when update trigger returns old tuple. This is a variant of the problem fixed in commit 25b692568, which unfortunately we failed to detect at the time. If an update trigger returns the "old" tuple, as it's entitled to do, then a subsequent iteration of the loop in ExecBRUpdateTriggers would have "oldtuple" equal to "trigtuple" and would fail to notice that it shouldn't free that.
In addition to fixing the code, extend the test case added by 25b692568 so that it covers multiple-trigger-iterations cases. This problem does not manifest in v12/HEAD, as a result of the relevant code having been largely rewritten for slotification. However, include the test case into v12/HEAD anyway, since this is clearly an area that someone could break again in future. Per report from Piotr Gabriel Kosinski. Back-patch into all supported branches, since the bug seems quite old. Diagnosis and code fix by Thomas Munro, test case by me. Discussion: https://postgr.es/m/CAFMLSdP0rd7LqC3j-H6Fh51FYSt5A10DDh-3=w4ppc4lluq...@mail.gmail.com Branch ------ REL_12_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/03813a50efa563f19110013b06e80f08d4f49cf5 Modified Files -------------- src/test/regress/expected/triggers.out | 70 ++++++++++++++++++++++++++++++++++ src/test/regress/sql/triggers.sql | 35 +++++++++++++++++ 2 files changed, 105 insertions(+)