postgres.git / summary / log / commit / refs

commit    c03fc84626beca122d4aafd77fe6eb508d98edb7
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 8d656aeebea..edc90e02dd2 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -224,6 +224,9 @@ create_plan_recurse(PlannerInfo *root, Path *best_path)
 {
 	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 c1c0c4e0d02..cd51d328c95 100644
--- a/src/backend/optimizer/prep/prepunion.c
+++ b/src/backend/optimizer/prep/prepunion.c
@@ -219,6 +219,9 @@ recurse_set_operations(Node *setOp, PlannerInfo *root,
 					   int flag, List *refnames_tlist,
 					   List **sortClauses, double *pNumGroups)
 {
+	/* Guard against stack overflow due to overly complex setop nests */
+	check_stack_depth();
+
 	if (IsA(setOp, RangeTblRef))
 	{
 		RangeTblRef *rtr = (RangeTblRef *) setOp;


[parent: e5e2cc6f8c1d]