postgres.git / summary / log / commit / refs

commit    d572003f74bb6bddac1c0eaf7fb5d0c4af1a3890
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Thu Dec 22 15:35:03 2022 +0000
First released in: 16.0, 11.19, 12.14, 13.10, 14.7, 15.2

    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


 src/backend/optimizer/prep/prepjointree.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/backend/optimizer/prep/prepjointree.c b/src/backend/optimizer/prep/prepjointree.c
index 1c20ef587ce..95bfe0f1573 100644
--- a/src/backend/optimizer/prep/prepjointree.c
+++ b/src/backend/optimizer/prep/prepjointree.c
@@ -26,6 +26,7 @@
 #include "postgres.h"
 
 #include "catalog/pg_type.h"
+#include "miscadmin.h"
 #include "nodes/makefuncs.h"
 #include "nodes/nodeFuncs.h"
 #include "optimizer/clauses.h"
@@ -230,6 +231,9 @@ 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;
@@ -715,6 +719,11 @@ pull_up_subqueries_recurse(PlannerInfo *root, Node *jtnode,
 						   JoinExpr *lowest_nulling_outer_join,
 						   AppendRelInfo *containing_appendrel)
 {
+	/* 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))
 	{
@@ -1761,6 +1770,9 @@ 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;


[parent: c8314d62a9bd]