From 15080a6725a940ea3ccb481898b99d53be388fc3 Mon Sep 17 00:00:00 2001 From: Bertrand Drouvot Date: Wed, 1 Jul 2026 05:43:07 +0000 Subject: [PATCH v1] Prevent crash when calling pgstat functions with unregistered stats kind If a custom statistics extension is loaded via CREATE EXTENSION without being listed in shared_preload_libraries, its _PG_init() skips the call to pgstat_register_kind(). The SQL functions are still created, and calling them invokes pgstat functions with a kind that was never registered. pgstat_get_kind_info() returns NULL in this case. The existing code only checked this via Assert() in some paths, so non-assert builds would dereference NULL and segfault. Add runtime checks in all public-facing pgstat functions that accept a PgStat_Kind and dereference the returned kind info: - pgstat_prep_pending_entry() - pgstat_fetch_entry() - pgstat_reset() - pgstat_reset_of_kind() - pgstat_have_entry() - pgstat_snapshot_fixed() - pgstat_init_entry() - pgstat_reset_entry() Each now raises ERROR with ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE when the kind is not known or registered. This affects any extension using the custom cumulative statistics API introduced in PG18. Author: Bertrand Drouvot Reviewed-by: Discussion: --- src/backend/utils/activity/pgstat.c | 45 ++++++++++++++++++++--- src/backend/utils/activity/pgstat_shmem.c | 13 ++++++- 2 files changed, 52 insertions(+), 6 deletions(-) 100.0% src/backend/utils/activity/ diff --git a/src/backend/utils/activity/pgstat.c b/src/backend/utils/activity/pgstat.c index c4fa14f138f..5180201c4e8 100644 --- a/src/backend/utils/activity/pgstat.c +++ b/src/backend/utils/activity/pgstat.c @@ -885,8 +885,13 @@ pgstat_reset(PgStat_Kind kind, Oid dboid, uint64 objid) const PgStat_KindInfo *kind_info = pgstat_get_kind_info(kind); TimestampTz ts = GetCurrentTimestamp(); + if (unlikely(kind_info == NULL)) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("statistics kind %u is not known or registered", kind))); + /* not needed atm, and doesn't make sense with the current signature */ - Assert(!pgstat_get_kind_info(kind)->fixed_amount); + Assert(!kind_info->fixed_amount); /* reset the "single counter" */ pgstat_reset_entry(kind, dboid, objid, ts); @@ -907,6 +912,11 @@ pgstat_reset_of_kind(PgStat_Kind kind) const PgStat_KindInfo *kind_info = pgstat_get_kind_info(kind); TimestampTz ts = GetCurrentTimestamp(); + if (unlikely(kind_info == NULL)) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("statistics kind %u is not known or registered", kind))); + if (kind_info->fixed_amount) kind_info->reset_all_cb(ts); else @@ -967,6 +977,11 @@ pgstat_fetch_entry(PgStat_Kind kind, Oid dboid, uint64 objid, bool *may_free) void *stats_data; const PgStat_KindInfo *kind_info = pgstat_get_kind_info(kind); + if (unlikely(kind_info == NULL)) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("statistics kind %u is not known or registered", kind))); + /* should be called from backends */ Assert(IsUnderPostmaster || !IsPostmasterEnvironment); Assert(!kind_info->fixed_amount); @@ -1088,8 +1103,15 @@ pgstat_get_stat_snapshot_timestamp(bool *have_snapshot) bool pgstat_have_entry(PgStat_Kind kind, Oid dboid, uint64 objid) { + const PgStat_KindInfo *kind_info = pgstat_get_kind_info(kind); + + if (unlikely(kind_info == NULL)) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("statistics kind %u is not known or registered", kind))); + /* fixed-numbered stats always exist */ - if (pgstat_get_kind_info(kind)->fixed_amount) + if (kind_info->fixed_amount) return true; return pgstat_get_entry_ref(kind, dboid, objid, false, NULL) != NULL; @@ -1104,8 +1126,15 @@ pgstat_have_entry(PgStat_Kind kind, Oid dboid, uint64 objid) void pgstat_snapshot_fixed(PgStat_Kind kind) { + const PgStat_KindInfo *kind_info = pgstat_get_kind_info(kind); + + if (unlikely(kind_info == NULL)) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("statistics kind %u is not known or registered", kind))); + Assert(pgstat_is_kind_valid(kind)); - Assert(pgstat_get_kind_info(kind)->fixed_amount); + Assert(kind_info->fixed_amount); if (force_stats_snapshot_clear) pgstat_clear_snapshot(); @@ -1310,9 +1339,15 @@ PgStat_EntryRef * pgstat_prep_pending_entry(PgStat_Kind kind, Oid dboid, uint64 objid, bool *created_entry) { PgStat_EntryRef *entry_ref; + const PgStat_KindInfo *kind_info = pgstat_get_kind_info(kind); + + if (unlikely(kind_info == NULL)) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("statistics kind %u is not known or registered", kind))); /* need to be able to flush out */ - Assert(pgstat_get_kind_info(kind)->flush_pending_cb != NULL); + Assert(kind_info->flush_pending_cb != NULL); if (unlikely(!pgStatPendingContext)) { @@ -1327,7 +1362,7 @@ pgstat_prep_pending_entry(PgStat_Kind kind, Oid dboid, uint64 objid, bool *creat if (entry_ref->pending == NULL) { - size_t entrysize = pgstat_get_kind_info(kind)->pending_size; + size_t entrysize = kind_info->pending_size; Assert(entrysize != (size_t) -1); diff --git a/src/backend/utils/activity/pgstat_shmem.c b/src/backend/utils/activity/pgstat_shmem.c index 5ea3f1973f9..4e6a556af93 100644 --- a/src/backend/utils/activity/pgstat_shmem.c +++ b/src/backend/utils/activity/pgstat_shmem.c @@ -318,6 +318,11 @@ pgstat_init_entry(PgStat_Kind kind, PgStatShared_Common *shheader; const PgStat_KindInfo *kind_info = pgstat_get_kind_info(kind); + if (unlikely(kind_info == NULL)) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("statistics kind %u is not known or registered", kind))); + /* * Initialize refcount to 1, marking it as valid / not dropped. The entry * can't be freed before the initialization because it can't be found as @@ -1127,8 +1132,14 @@ void pgstat_reset_entry(PgStat_Kind kind, Oid dboid, uint64 objid, TimestampTz ts) { PgStat_EntryRef *entry_ref; + const PgStat_KindInfo *kind_info = pgstat_get_kind_info(kind); + + if (unlikely(kind_info == NULL)) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("statistics kind %u is not known or registered", kind))); - Assert(!pgstat_get_kind_info(kind)->fixed_amount); + Assert(!kind_info->fixed_amount); entry_ref = pgstat_get_entry_ref(kind, dboid, objid, false, NULL); if (!entry_ref || entry_ref->shared_entry->dropped) -- 2.34.1