Check stack depth in new recursive functions

alvherre · alvherre · commit b0f7dd915bca · 2023-11-08T18:44:54.000+01:00
Commit b0e96f3 introduced a bunch of recursive functions, but failed to make them check for stack depth. This can cause the backend to crash when operating on inheritance hierarchies several thousands deep. Protect the code by adding the missing stack depth checks. Reported-by: Alexander Lakhin <exclusion@gmail.com> Discussion: https://postgr.es/m/b2ac2392-9727-5f76-e890-721ac80c1615@gmail.com
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
@@ -7630,6 +7630,9 @@ set_attnotnull(List **wqueue, Relation rel, AttrNumber attnum, bool recurse,
 	Form_pg_attribute attForm;
 	bool		retval = false;
 
+	/* Guard against stack overflow due to overly deep inheritance tree. */
+	check_stack_depth();
+
 	tuple = SearchSysCacheCopyAttNum(RelationGetRelid(rel), attnum);
 	if (!HeapTupleIsValid(tuple))
 		elog(ERROR, "cache lookup failed for attribute %d of relation %u",
@@ -7716,6 +7719,9 @@ ATExecSetNotNull(List **wqueue, Relation rel, char *conName, char *colName,
 	bool		is_no_inherit = false;
 	List	   *ready = NIL;
 
+	/* Guard against stack overflow due to overly deep inheritance tree. */
+	check_stack_depth();
+
 	/*
 	 * In cases of multiple inheritance, we might visit the same child more
 	 * than once.  In the topmost call, set up a list that we fill with all
@@ -9359,6 +9365,9 @@ ATAddCheckNNConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
 	ListCell   *child;
 	ObjectAddress address = InvalidObjectAddress;
 
+	/* Guard against stack overflow due to overly deep inheritance tree. */
+	check_stack_depth();
+
 	/* At top level, permission check was done in ATPrepCmd, else do it */
 	if (recursing)
 		ATSimplePermissions(AT_AddConstraint, rel, ATT_TABLE | ATT_FOREIGN_TABLE);
@@ -12428,6 +12437,9 @@ dropconstraint_internal(Relation rel, HeapTuple constraintTup, DropBehavior beha
 		return InvalidObjectAddress;
 	*readyRels = lappend_oid(*readyRels, RelationGetRelid(rel));
 
+	/* Guard against stack overflow due to overly deep inheritance tree. */
+	check_stack_depth();
+
 	/* At top level, permission check was done in ATPrepCmd, else do it */
 	if (recursing)
 		ATSimplePermissions(AT_DropConstraint, rel, ATT_TABLE | ATT_FOREIGN_TABLE);
