pg_trgm: fix crash in 2-item picksplit
Whether from size overflow in gistSplit or from secondary splits,
picksplit is (rarely) called with exactly two items to split.
Formerly, due to special-case handling of the last item, this would
lead to access to an uninitialized cache entry; prior to PG 13 this
might have been harmless or at worst led to an incorrect union datum,
but in 13 onwards it can cause a backend crash from using an
uninitialized pointer.
Repair by removing the special case, which was deemed not to have been
appropriate anyway. Backpatch all the way, because this bug has
existed since pg_trgm was added.
Per report on IRC from user "ftzdomino". Analysis and testing by me,
patch from Alexander Korotkov.
Discussion: https://postgr.es/m/87k0usfdxg.fsf@news-spur.riddles.org.uk
Branch
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REL9_5_STABLE
Details
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https://git.postgresql.org/pg/commitdiff/4b212b7c87754095d4f89b03a3aaec6e32d09342
Modified Files
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contrib/pg_trgm/trgm_gist.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)
