From edd9a2bf741be95aa771b9fcacb2ce7378fb9121 Mon Sep 17 00:00:00 2001 From: Jeff Davis Date: Fri, 9 Jul 2021 14:15:48 -0700 Subject: [PATCH] Fix assign_record_type_typmod(). If an error occurred in the wrong place, it was possible to leave an unintialized entry in the hash table, leading to a crash. Fixed. Also, be more careful about the order of operations so that an allocation error doesn't leak memory in CacheMemoryContext or unnecessarily advance NextRecordTypmod. Backpatch through version 11. Earlier versions (prior to 35ea75632a5) do not exhibit the problem, because an uninitialized hash entry contains a valid empty list. Author: Sait Talha Nisanci Reviewed-by: Andres Freund Discussion: https://postgr.es/m/HE1PR8303MB009069D476225B9A9E194B8891779@HE1PR8303MB0090.EURPRD83.prod.outlook.com Backpatch-through: 11 --- src/backend/utils/cache/typcache.c | 28 +++++++++++++++++++++++----- 1 file changed, 23 insertions(+), 5 deletions(-) diff --git a/src/backend/utils/cache/typcache.c b/src/backend/utils/cache/typcache.c index c848d09d14..5d4d5660d9 100644 --- a/src/backend/utils/cache/typcache.c +++ b/src/backend/utils/cache/typcache.c @@ -1855,10 +1855,14 @@ assign_record_type_typmod(TupleDesc tupDesc) CreateCacheMemoryContext(); } - /* Find or create a hashtable entry for this tuple descriptor */ + /* + * Find a hashtable entry for this tuple descriptor. We don't use + * HASH_ENTER yet, because if it's missing, we need to make sure that all + * the allocations succeed before we create the new entry. + */ recentry = (RecordCacheEntry *) hash_search(RecordCacheHash, (void *) &tupDesc, - HASH_ENTER, &found); + HASH_FIND, &found); if (found && recentry->tupdesc != NULL) { tupDesc->tdtypmod = recentry->tupdesc->tdtypmod; @@ -1866,25 +1870,39 @@ assign_record_type_typmod(TupleDesc tupDesc) } /* Not present, so need to manufacture an entry */ - recentry->tupdesc = NULL; oldcxt = MemoryContextSwitchTo(CacheMemoryContext); /* Look in the SharedRecordTypmodRegistry, if attached */ entDesc = find_or_make_matching_shared_tupledesc(tupDesc); if (entDesc == NULL) { + /* + * Make sure we have room before we CreateTupleDescCopy() or advance + * NextRecordTypmod. + */ + ensure_record_cache_typmod_slot_exists(NextRecordTypmod); + /* Reference-counted local cache only. */ entDesc = CreateTupleDescCopy(tupDesc); entDesc->tdrefcount = 1; entDesc->tdtypmod = NextRecordTypmod++; } - ensure_record_cache_typmod_slot_exists(entDesc->tdtypmod); + else + { + ensure_record_cache_typmod_slot_exists(entDesc->tdtypmod); + } + RecordCacheArray[entDesc->tdtypmod] = entDesc; - recentry->tupdesc = entDesc; /* Assign a unique tupdesc identifier, too. */ RecordIdentifierArray[entDesc->tdtypmod] = ++tupledesc_id_counter; + /* Fully initialized; create the hash table entry */ + recentry = (RecordCacheEntry *) hash_search(RecordCacheHash, + (void *) &tupDesc, + HASH_ENTER, NULL); + recentry->tupdesc = entDesc; + /* Update the caller's tuple descriptor. */ tupDesc->tdtypmod = entDesc->tdtypmod;