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pgsql: Fix crash on trying to expand a shared memory hash table 2+ messages / 1 participants [nested] [flat]
* pgsql: Fix crash on trying to expand a shared memory hash table @ 2026-08-25 11:12 Heikki Linnakangas <heikki.linnakangas@iki.fi> 0 siblings, 0 replies; 2+ messages in thread From: Heikki Linnakangas @ 2026-08-25 11:12 UTC (permalink / raw) To: pgsql-committers@lists.postgresql.org Fix crash on trying to expand a shared memory hash table When a hash table grows large enough we try to expand the directory, but we shouldn't try to do that if the hash table is marked as HASH_FIXED_SIZE. Before commit 9fe9ecd516b that was harmless, although it was a little weird to expand the directory when allocating the new element was doomed to fail later anyway. But the new allocator function added in that commit for shared memory hash tables did not expect to be called after hash table creation at all and would just crash. Fix by ensuring that the allocator is not called after hash table creation for HASH_FIXED_SIZE tables. The crash started with commit 9fe9ecd516b in v19, so backpatch to v19. To trigger the crash, you needed a shared memory hash table of just the right size so that we would attempt to resize it: power-of-2 and at least HASH_SEGSIZE (256) elements. With any other size, you would run out of allocated elements first. Author: Konstantin Knizhnik <knizhnik@garret.ru> Reviewed-by: Rahila Syed <rahilasyed90@gmail.com> Discussion: https://www.postgresql.org/message-id/d59221f2-b3d2-41ad-8bf0-d581b42e4cba@garret.ru Backpatch-through: 19 Branch ------ REL_19_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/31ad154242e2dc9fa9bbc4ebbe31f559e2282d9c Modified Files -------------- src/backend/utils/hash/dynahash.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) ^ permalink raw reply [nested|flat] 2+ messages in thread
* pgsql: Fix crash on trying to expand a shared memory hash table @ 2026-08-25 11:12 Heikki Linnakangas <heikki.linnakangas@iki.fi> 0 siblings, 0 replies; 2+ messages in thread From: Heikki Linnakangas @ 2026-08-25 11:12 UTC (permalink / raw) To: pgsql-committers@lists.postgresql.org Fix crash on trying to expand a shared memory hash table When a hash table grows large enough we try to expand the directory, but we shouldn't try to do that if the hash table is marked as HASH_FIXED_SIZE. Before commit 9fe9ecd516b that was harmless, although it was a little weird to expand the directory when allocating the new element was doomed to fail later anyway. But the new allocator function added in that commit for shared memory hash tables did not expect to be called after hash table creation at all and would just crash. Fix by ensuring that the allocator is not called after hash table creation for HASH_FIXED_SIZE tables. The crash started with commit 9fe9ecd516b in v19, so backpatch to v19. To trigger the crash, you needed a shared memory hash table of just the right size so that we would attempt to resize it: power-of-2 and at least HASH_SEGSIZE (256) elements. With any other size, you would run out of allocated elements first. Author: Konstantin Knizhnik <knizhnik@garret.ru> Reviewed-by: Rahila Syed <rahilasyed90@gmail.com> Discussion: https://www.postgresql.org/message-id/d59221f2-b3d2-41ad-8bf0-d581b42e4cba@garret.ru Backpatch-through: 19 Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/86481d9f4930750a9c62c25216bf7783f69d6ff0 Modified Files -------------- src/backend/utils/hash/dynahash.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) ^ permalink raw reply [nested|flat] 2+ messages in thread
end of thread, other threads:[~2026-08-25 11:12 UTC | newest] Thread overview: 2+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2026-08-25 11:12 pgsql: Fix crash on trying to expand a shared memory hash table Heikki Linnakangas <heikki.linnakangas@iki.fi> 2026-08-25 11:12 pgsql: Fix crash on trying to expand a shared memory hash table Heikki Linnakangas <heikki.linnakangas@iki.fi>
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