Fix uninitialized slot array access during the upgrade.

Amit Kapila · Amit Kapila · commit a7db71ed2787 · 2023-11-09T09:26:40.000+05:30
Commit 29d0a77 introduced fetching slot information from the old cluster but didn't initialize the required array in all the code paths. So when trying to access the array in verbose mode for the new cluster, it leads to an uninitialized memory access. Author: Vignesh C Discussion: http://postgr.es/m/CALDaNm1tntGP5=CtMz=v+k3_PGv7kE9t6iWSgX-QiurAaFkhZw@mail.gmail.com
diff --git a/src/bin/pg_upgrade/info.c b/src/bin/pg_upgrade/info.c
@@ -408,7 +408,7 @@ get_db_infos(ClusterInfo *cluster)
 	i_spclocation = PQfnumber(res, "spclocation");
 
 	ntups = PQntuples(res);
-	dbinfos = (DbInfo *) pg_malloc(sizeof(DbInfo) * ntups);
+	dbinfos = (DbInfo *) pg_malloc0(sizeof(DbInfo) * ntups);
 
 	for (tupnum = 0; tupnum < ntups; tupnum++)
 	{
@@ -636,15 +636,11 @@ get_old_cluster_logical_slot_infos(DbInfo *dbinfo, bool live_check)
 	PGconn	   *conn;
 	PGresult   *res;
 	LogicalSlotInfo *slotinfos = NULL;
-	int			num_slots = 0;
+	int			num_slots;
 
 	/* Logical slots can be migrated since PG17. */
 	if (GET_MAJOR_VERSION(old_cluster.major_version) <= 1600)
-	{
-		dbinfo->slot_arr.slots = slotinfos;
-		dbinfo->slot_arr.nslots = num_slots;
 		return;
-	}
 
 	conn = connectToServer(&old_cluster, dbinfo->db_name);
 
