Prevent a rowtype from being included in itself.

Eventually we might be able to allow that, but it's not clear how many
places need to be fixed to prevent infinite recursion when there's a direct
or indirect inclusion of a rowtype in itself.  One such place is
CheckAttributeType(), which will recurse to stack overflow in cases such as
those exhibited in bug #5950 from Alex Perepelica.  If we were sure it was
the only such place, we could easily modify the code added by this patch to
stop the recursion without a complaint ... but it probably isn't the only
such place.  Hence, throw error until such time as someone is excited
enough about this type of usage to put work into making it safe.

Back-patch as far as 8.3.  8.2 doesn't have the recursive call in
CheckAttributeType in the first place, so I see no need to add code there
in the absence of clear evidence of a problem elsewhere.

5 files changed, 66 insertions, 7 deletions

diff --git a/src/backend/catalog/heap.c b/src/backend/catalog/heap.c
index 9efef44778..edc5427341 100644
--- a/src/backend/catalog/heap.c
+++ b/src/backend/catalog/heap.c
@@ -388,7 +388,8 @@ CheckAttributeNamesTypes(TupleDesc tupdesc, char relkind)
 	for (i = 0; i < natts; i++)
 	{
 		CheckAttributeType(NameStr(tupdesc->attrs[i]->attname),
-						   tupdesc->attrs[i]->atttypid);
+						   tupdesc->attrs[i]->atttypid,
+						   NIL /* assume we're creating a new rowtype */);
 	}
 }
 
@@ -396,14 +397,23 @@ CheckAttributeNamesTypes(TupleDesc tupdesc, char relkind)
  *		CheckAttributeType
  *
  *		Verify that the proposed datatype of an attribute is legal.
- *		This is needed because there are types (and pseudo-types)
+ *		This is needed mainly because there are types (and pseudo-types)
  *		in the catalogs that we do not support as elements of real tuples.
+ *		We also check some other properties required of a table column.
+ *
+ * If the attribute is being proposed for addition to an existing table or
+ * composite type, pass a one-element list of the rowtype OID as
+ * containing_rowtypes.  When checking a to-be-created rowtype, it's
+ * sufficient to pass NIL, because there could not be any recursive reference
+ * to a not-yet-existing rowtype.
  * --------------------------------
  */
 void
-CheckAttributeType(const char *attname, Oid atttypid)
+CheckAttributeType(const char *attname, Oid atttypid,
+				   List *containing_rowtypes)
 {
 	char		att_typtype = get_typtype(atttypid);
+	Oid			att_typelem;
 
 	if (atttypid == UNKNOWNOID)
 	{
@@ -439,6 +449,20 @@ CheckAttributeType(const char *attname, Oid atttypid)
 		TupleDesc	tupdesc;
 		int			i;
 
+		/*
+		 * Check for self-containment.  Eventually we might be able to allow
+		 * this (just return without complaint, if so) but it's not clear how
+		 * many other places would require anti-recursion defenses before it
+		 * would be safe to allow tables to contain their own rowtype.
+		 */
+		if (list_member_oid(containing_rowtypes, atttypid))
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
+					 errmsg("composite type %s cannot be made a member of itself",
+							format_type_be(atttypid))));
+
+		containing_rowtypes = lcons_oid(atttypid, containing_rowtypes);
+
 		relation = relation_open(get_typ_typrelid(atttypid), AccessShareLock);
 
 		tupdesc = RelationGetDescr(relation);
@@ -449,10 +473,21 @@ CheckAttributeType(const char *attname, Oid atttypid)
 
 			if (attr->attisdropped)
 				continue;
-			CheckAttributeType(NameStr(attr->attname), attr->atttypid);
+			CheckAttributeType(NameStr(attr->attname), attr->atttypid,
+							   containing_rowtypes);
 		}
 
 		relation_close(relation, AccessShareLock);
+
+		containing_rowtypes = list_delete_first(containing_rowtypes);
+	}
+	else if (OidIsValid((att_typelem = get_element_type(atttypid))))
+	{
+		/*
+		 * Must recurse into array types, too, in case they are composite.
+		 */
+		CheckAttributeType(attname, att_typelem,
+						   containing_rowtypes);
 	}
 }
 
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 14757befdf..4e3e04d077 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -3119,7 +3119,8 @@ ATExecAddColumn(AlteredTableInfo *tab, Relation rel,
 	typeOid = HeapTupleGetOid(typeTuple);
 
 	/* make sure datatype is legal for a column */
-	CheckAttributeType(colDef->colname, typeOid);
+	CheckAttributeType(colDef->colname, typeOid,
+					   list_make1_oid(rel->rd_rel->reltype));
 
 	attributeTuple = heap_addheader(Natts_pg_attribute,
 									false,
@@ -4818,7 +4819,8 @@ ATPrepAlterColumnType(List **wqueue,
 	targettype = typenameTypeId(NULL, typename, &targettypmod);
 
 	/* make sure datatype is legal for a column */
-	CheckAttributeType(colName, targettype);
+	CheckAttributeType(colName, targettype,
+					   list_make1_oid(rel->rd_rel->reltype));
 
 	/*
 	 * Set up an expression to transform the old data value to the new type.
diff --git a/src/include/catalog/heap.h b/src/include/catalog/heap.h
index 727af295c7..678c11e7f6 100644
--- a/src/include/catalog/heap.h
+++ b/src/include/catalog/heap.h
@@ -98,6 +98,7 @@ extern Form_pg_attribute SystemAttributeByName(const char *attname,
 
 extern void CheckAttributeNamesTypes(TupleDesc tupdesc, char relkind);
 
-extern void CheckAttributeType(const char *attname, Oid atttypid);
+extern void CheckAttributeType(const char *attname, Oid atttypid,
+							   List *containing_rowtypes);
 
 #endif   /* HEAP_H */
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index 51d5afa81f..a6e4eeaaa3 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -1384,6 +1384,18 @@ select * from another;
 (3 rows)
 
 drop table another;
+-- disallow recursive containment of row types
+create temp table recur1 (f1 int);
+alter table recur1 add column f2 recur1; -- fails
+ERROR:  composite type recur1 cannot be made a member of itself
+alter table recur1 add column f2 recur1[]; -- fails
+ERROR:  composite type recur1 cannot be made a member of itself
+create temp table recur2 (f1 int, f2 recur1);
+alter table recur1 add column f2 recur2; -- fails
+ERROR:  composite type recur1 cannot be made a member of itself
+alter table recur1 add column f2 int;
+alter table recur1 alter column f2 type recur2; -- fails
+ERROR:  composite type recur1 cannot be made a member of itself
 --
 -- alter function
 --
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index 81cc70612d..c6ce7ae4db 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -1045,6 +1045,15 @@ select * from another;
 
 drop table another;
 
+-- disallow recursive containment of row types
+create temp table recur1 (f1 int);
+alter table recur1 add column f2 recur1; -- fails
+alter table recur1 add column f2 recur1[]; -- fails
+create temp table recur2 (f1 int, f2 recur1);
+alter table recur1 add column f2 recur2; -- fails
+alter table recur1 add column f2 int;
+alter table recur1 alter column f2 type recur2; -- fails
+
 --
 -- alter function
 --