From: Tomas Vondra <tomas.vondra@postgresql.org>
Date: Sun, 23 Jan 2022 01:49:41 +0000 (+0100)
Subject: Check syscache result in AlterStatistics
X-Git-Tag: REL_15_BETA1~849
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=6d554e3fcd6fb8be2dbcbd3521e2947ed7a552cb;p=thirdparty%2Fpostgresql.git

Check syscache result in AlterStatistics

The syscache lookup may return NULL even for valid OID, for example due
to a concurrent DROP STATISTICS, so a HeapTupleIsValid is necessary.
Without it, it may fail with a segfault.

Reported by Alexander Lakhin, patch by me. Backpatch to 13, where ALTER
STATISTICS ... SET STATISTICS was introduced.

Backpatch-through: 13
Discussion: https://postgr.es/m/17372-bf3b6e947e35ae77%40postgresql.org
---

diff --git a/src/backend/commands/statscmds.c b/src/backend/commands/statscmds.c
index f7419b8f562..54a190722df 100644
--- a/src/backend/commands/statscmds.c
+++ b/src/backend/commands/statscmds.c
@@ -657,6 +657,8 @@ AlterStatistics(AlterStatsStmt *stmt)
 	rel = table_open(StatisticExtRelationId, RowExclusiveLock);
 
 	oldtup = SearchSysCache1(STATEXTOID, ObjectIdGetDatum(stxoid));
+	if (!HeapTupleIsValid(oldtup))
+		elog(ERROR, "cache lookup failed for extended statistics object %u", stxoid);
 
 	/* Must be owner of the existing statistics object */
 	if (!pg_statistics_object_ownercheck(stxoid, GetUserId()))