pgq.triggers: Fix potential rare crash.

The bad hash_search(HASH_ENTER) + SPI_execute() pattern
is used here also.  Fix it by always properly initializing
the info structure.

The similar pattern exist also in PgqTriggerInfo, but that
is already handled via ->finalized flag.

2 files changed, 39 insertions, 10 deletions

diff --git a/sql/pgq/triggers/common.c b/sql/pgq/triggers/common.c
index 4bbdd9b2..676c0fc2 100644
--- a/sql/pgq/triggers/common.c
+++ b/sql/pgq/triggers/common.c
@@ -275,9 +275,6 @@ static void fill_tbl_info(Relation rel, struct PgqTableInfo *info)
 	bool isnull;
 	int res, i, attno;
 
-	/* allow reset ASAP, but ignore it in this call */
-	info->invalid = false;
-
 	/* load pkeys */
 	values[0] = ObjectIdGetDatum(rel->rd_id);
 	res = SPI_execute_plan(pkey_plan, values, NULL, false, 0);
@@ -308,10 +305,14 @@ static void fill_tbl_info(Relation rel, struct PgqTableInfo *info)
 	info->tg_cache = NULL;
 }
 
-static void free_info(struct PgqTableInfo *info)
+static void clean_info(struct PgqTableInfo *info, bool found)
 {
 	struct PgqTriggerInfo *tg, *tmp = info->tg_cache;
 	int i;
+
+	if (!found)
+		goto uninitialized;
+
 	for (tg = info->tg_cache; tg; ) {
 		tmp = tg->next;
 		if (tg->ignore_list)
@@ -325,9 +326,20 @@ static void free_info(struct PgqTableInfo *info)
 		pfree(tg);
 		tg = tmp;
 	}
-	pfree(info->table_name);
-	pfree(info->pkey_attno);
-	pfree((void *)info->pkey_list);
+	if (info->table_name)
+		pfree(info->table_name);
+	if (info->pkey_attno)
+		pfree(info->pkey_attno);
+	if (info->pkey_list)
+		pfree((void *)info->pkey_list);
+
+uninitialized:
+	info->tg_cache = NULL;
+	info->table_name = NULL;
+	info->pkey_attno = NULL;
+	info->pkey_list = NULL;
+	info->n_pkeys = 0;
+	info->invalid = true;
 }
 
 /*
@@ -358,9 +370,26 @@ static struct PgqTableInfo *find_table_info(Relation rel)
 
 	entry = hash_search(tbl_cache_map, &rel->rd_id, HASH_ENTER, &found);
 	if (!found || entry->invalid) {
-		if (found)
-			free_info(entry);
+		clean_info(entry, found);
+
+		/*
+		 * During fill_tbl_info() 2 events can happen:
+		 * - table info reset
+		 * - exception
+		 * To survive both, always clean struct and tag
+		 * as invalid but differently from reset.
+		 */
+		entry->invalid = 2;
+
+		/* find info */
 		fill_tbl_info(rel, entry);
+
+		/*
+		 * If no reset happened, it's valid.  Actual reset
+		 * is postponed to next call.
+		 */
+		if (entry->invalid == 2)
+			entry->invalid = false;
 	}
 
 	return entry;
diff --git a/sql/pgq/triggers/common.h b/sql/pgq/triggers/common.h
index 310002ca..0192c493 100644
--- a/sql/pgq/triggers/common.h
+++ b/sql/pgq/triggers/common.h
@@ -73,7 +73,7 @@ struct PgqTableInfo {
 	const char *pkey_list;	/* pk column name list */
 	int *pkey_attno;	/* pk column positions */
 	char *table_name;	/* schema-quelified table name */
-	bool invalid;		/* set if the info was invalidated */
+	int invalid;		/* set if the info was invalidated */
 
 	struct PgqTriggerInfo *tg_cache;
 };