From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Thu, 22 Dec 2022 15:35:03 +0000 (-0500)
Subject: Add some recursion and looping defenses in prepjointree.c.
X-Git-Tag: REL_11_19~25
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=8cd700cc5a676282912c7080cfa142977a2dd851;p=thirdparty%2Fpostgresql.git

Add some recursion and looping defenses in prepjointree.c.

Andrey Lepikhov demonstrated a case where we spend an unreasonable
amount of time in pull_up_subqueries().  Not only is that recursing
with no explicit check for stack overrun, but the code seems not
interruptable by control-C.  Let's stick a CHECK_FOR_INTERRUPTS
there, along with sprinkling some stack depth checks.

An actual fix for the excessive time consumption seems a bit
risky to back-patch; but this isn't, so let's do so.

Discussion: https://postgr.es/m/703c09a2-08f3-d2ec-b33d-dbecd62428b8@postgrespro.ru
---

diff --git a/src/backend/optimizer/prep/prepjointree.c b/src/backend/optimizer/prep/prepjointree.c
index fe1149ee4bf..e3c62cb3481 100644
--- a/src/backend/optimizer/prep/prepjointree.c
+++ b/src/backend/optimizer/prep/prepjointree.c
@@ -24,6 +24,7 @@
 #include "postgres.h"
 
 #include "catalog/pg_type.h"
+#include "miscadmin.h"
 #include "nodes/makefuncs.h"
 #include "nodes/nodeFuncs.h"
 #include "optimizer/clauses.h"
@@ -178,6 +179,9 @@ static Node *
 pull_up_sublinks_jointree_recurse(PlannerInfo *root, Node *jtnode,
 								  Relids *relids)
 {
+	/* Since this function recurses, it could be driven to stack overflow. */
+	check_stack_depth();
+
 	if (jtnode == NULL)
 	{
 		*relids = NULL;
@@ -677,6 +681,11 @@ pull_up_subqueries_recurse(PlannerInfo *root, Node *jtnode,
 						   AppendRelInfo *containing_appendrel,
 						   bool deletion_ok)
 {
+	/* Since this function recurses, it could be driven to stack overflow. */
+	check_stack_depth();
+	/* Also, since it's a bit expensive, let's check for query cancel. */
+	CHECK_FOR_INTERRUPTS();
+
 	Assert(jtnode != NULL);
 	if (IsA(jtnode, RangeTblRef))
 	{
@@ -1824,6 +1833,9 @@ is_simple_union_all(Query *subquery)
 static bool
 is_simple_union_all_recurse(Node *setOp, Query *setOpQuery, List *colTypes)
 {
+	/* Since this function recurses, it could be driven to stack overflow. */
+	check_stack_depth();
+
 	if (IsA(setOp, RangeTblRef))
 	{
 		RangeTblRef *rtr = (RangeTblRef *) setOp;