8000 Fix misbehavior in contrib/pg_trgm with an unsatisfiable regex. · postgres/postgres@b183274 · GitHub
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Fix misbehavior in contrib/pg_trgm with an unsatisfiable regex.
If the regex compiler can see that a regex is unsatisfiable (for example, '$foo') then it may emit an NFA having no arcs. pg_trgm's packGraph function did the wrong thing in this case; it would access off the end of a work array, and with bad luck could produce a corrupted output data structure causing more problems later. This could end with wrong answers or crashes in queries using a pg_trgm GIN or GiST index with such a regex. Fix by not trying to de-duplicate if there aren't at least 2 arcs. Per bug #17830 from Alexander Lakhin. Back-patch to all supported branches. Discussion: https://postgr.es/m/17830-57ff5f89bdb02b09@postgresql.org
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+25
-10
lines changed

3 files changed

+25
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lines changed

‎contrib/pg_trgm/expected/pg_word_trgm.out

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@@ -1042,3 +1042,9 @@ select t,word_similarity('Kabankala',t) as sml from test_trgm2 where t %> 'Kaban
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Waikala | 0.3
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(89 rows)
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-- test unsatisfiable pattern
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select * from test_trgm2 where t ~ '.*$x';
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t
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---
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(0 rows)
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‎contrib/pg_trgm/sql/pg_word_trgm.sql

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@@ -40,3 +40,6 @@ select t,word_similarity('Baykal',t) as sml from test_trgm2 where 'Baykal' <% t
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select t,word_similarity('Kabankala',t) as sml from test_trgm2 where 'Kabankala' <% t order by sml desc, t;
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select t,word_similarity('Baykal',t) as sml from test_trgm2 where t %> 'Baykal' order by sml desc, t;
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select t,word_similarity('Kabankala',t) as sml from test_trgm2 where t %> 'Kabankala' order by sml desc, t;
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-- test unsatisfiable pattern
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select * from test_trgm2 where t ~ '.*$x';

‎contrib/pg_trgm/trgm_regexp.c

Lines changed: 16 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -1935,9 +1935,7 @@ packGraph(TrgmNFA *trgmNFA, MemoryContext rcontext)
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arcsCount;
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HASH_SEQ_STATUS scan_status;
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TrgmState *state;
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TrgmPackArcInfo *arcs,
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*p1,
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*p2;
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TrgmPackArcInfo *arcs;
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TrgmPackedArc *packedArcs;
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TrgmPackedGraph *result;
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int i,
@@ -2009,17 +2007,25 @@ packGraph(TrgmNFA *trgmNFA, MemoryContext rcontext)
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qsort(arcs, arcIndex, sizeof(TrgmPackArcInfo), packArcInfoCmp);
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/* We could have duplicates because states were merged. Remove them. */
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/* p1 is probe point, p2 is last known non-duplicate. */
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p2 = arcs;
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for (p1 = arcs + 1; p1 < arcs + arcIndex; p1++)
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if (arcIndex > 1)
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{
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if (packArcInfoCmp(p1, p2) > 0)
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/* p1 is probe point, p2 is last known non-duplicate. */
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TrgmPackArcInfo *p1,
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*p2;
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p2 = arcs;
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for (p1 = arcs + 1; p1 < arcs + arcIndex; p1++)
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{
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p2++;
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*p2 = *p1;
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if (packArcInfoCmp(p1, p2) > 0)
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{
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p2++;
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*p2 = *p1;
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}
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}
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arcsCount = (p2 - arcs) + 1;
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}
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arcsCount = (p2 - arcs) + 1;
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else
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arcsCount = arcIndex;
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/* Create packed representation */
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result = (TrgmPackedGraph *)

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