postgres.git / summary / log / commit / refs

commit    4e9fb4bfe2e33aff941e29ec55972d68f4cdb69c
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Sun Jan 28 18:39:07 2018 +0000
First released in: 11.0, 9.3.21, 9.4.16, 9.5.11, 9.6.7, 10.2

    Add stack-overflow guards in set-operation planning.
    
    create_plan_recurse lacked any stack depth check.  This is not per
    our normal coding rules, but I'd supposed it was safe because earlier
    planner processing is more complex and presumably should eat more
    stack.  But bug #15033 from Andrew Grossman shows this isn't true,
    at least not for queries having the form of a many-thousand-way
    INTERSECT stack.
    
    Further testing showed that recurse_set_operations is also capable
    of being crashed in this way, since it likewise will recurse to the
    bottom of a parsetree before calling any support functions that
    might themselves contain any stack checks.  However, its stack
    consumption is only perhaps a third of create_plan_recurse's.
    
    It's possible that this particular problem with create_plan_recurse can
    only manifest in 9.6 and later, since before that we didn't build a Path
    tree for set operations.  But having seen this example, I now have no
    faith in the proposition that create_plan_recurse doesn't need a stack
    check, so back-patch to all supported branches.
    
    Discussion: https://postgr.es/m/20180127050845.28812.58244@wrigleys.postgresql.org


 src/backend/optimizer/plan/createplan.c | 3 +++
 src/backend/optimizer/prep/prepunion.c  | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index e230329a452..5de9235f5dd 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -343,6 +343,9 @@ create_plan_recurse(PlannerInfo *root, Path *best_path, int flags)
 {
 	Plan	   *plan;
 
+	/* Guard against stack overflow due to overly complex plans */
+	check_stack_depth();
+
 	switch (best_path->pathtype)
 	{
 		case T_SeqScan:
diff --git a/src/backend/optimizer/prep/prepunion.c b/src/backend/optimizer/prep/prepunion.c
index 266ee4db5e8..1d61a0d616f 100644
--- a/src/backend/optimizer/prep/prepunion.c
+++ b/src/backend/optimizer/prep/prepunion.c
@@ -253,6 +253,9 @@ recurse_set_operations(Node *setOp, PlannerInfo *root,
 					   List **pTargetList,
 					   double *pNumGroups)
 {
+	/* Guard against stack overflow due to overly complex setop nests */
+	check_stack_depth();
+
 	if (IsA(setOp, RangeTblRef))
 	{
 		RangeTblRef *rtr = (RangeTblRef *) setOp;


[parent: 462402be873d]