Defend against self-referential views in relation_is_updatable().

While a self-referential view doesn't actually work, it's possible
to create one, and it turns out that this breaks some of the
information_schema views.  Those views call relation_is_updatable(),
which neglected to consider the hazards of being recursive.  In
older PG versions you get a "stack depth limit exceeded" error,
but since v10 it'd recurse to the point of stack overrun and crash,
because commit a4c35ea1c took out the expression_returns_set() call
that was incidentally checking the stack depth.

Since this function is only used by information_schema views, it
seems like it'd be better to return "not updatable" than suffer
an error.  Hence, add tracking of what views we're examining,
in just the same way that the nearby fireRIRrules() code detects
self-referential views.  I added a check_stack_depth() call too,
just to be defensive.

Per private report from Manuel Rigger.  Back-patch to all
supported versions.

diff --git a/src/backend/rewrite/rewriteHandler.c b/src/backend/rewrite/rewriteHandler.c
index 53952cd9791e33bb26d08b0f9b9e52d2457a4c6b..60cb50e8405795b00a81655bb49e15c9dd0a7604 100644 (file)
--- a/src/backend/rewrite/rewriteHandler.c
+++ b/src/backend/rewrite/rewriteHandler.c
@@ -25,6 +25,7 @@
 #include "catalog/pg_type.h"
 #include "commands/trigger.h"
 #include "foreign/fdwapi.h"
+#include "miscadmin.h"
 #include "nodes/makefuncs.h"
 #include "nodes/nodeFuncs.h"
 #include "parser/analyze.h"
@@ -2582,6 +2583,11 @@ view_cols_are_auto_updatable(Query *viewquery,
  * non-NULL, then only the specified columns are considered when testing for
  * updatability.
  *
+ * Unlike the preceding functions, this does recurse to look at a view's
+ * base relations, so it needs to detect recursion.  To do that, we pass
+ * a list of currently-considered outer relations.  External callers need
+ * only pass NIL.
+ *
  * This is used for the information_schema views, which have separate concepts
  * of "updatable" and "trigger updatable".  A relation is "updatable" if it
  * can be updated without the need for triggers (either because it has a
@@ -2600,6 +2606,7 @@ view_cols_are_auto_updatable(Query *viewquery,
  */
 int
 relation_is_updatable(Oid reloid,
+                     List *outer_reloids,
                      bool include_triggers,
                      Bitmapset *include_cols)
 {
@@ -2609,6 +2616,9 @@ relation_is_updatable(Oid reloid,
 
 #define ALL_EVENTS ((1 << CMD_INSERT) | (1 << CMD_UPDATE) | (1 << CMD_DELETE))
 
+   /* Since this function recurses, it could be driven to stack overflow */
+   check_stack_depth();
+
    rel = try_relation_open(reloid, AccessShareLock);
 
    /*
@@ -2620,6 +2630,13 @@ relation_is_updatable(Oid reloid,
    if (rel == NULL)
        return 0;
 
+   /* If we detect a recursive view, report that it is not updatable */
+   if (list_member_oid(outer_reloids, RelationGetRelid(rel)))
+   {
+       relation_close(rel, AccessShareLock);
+       return 0;
+   }
+
    /* If the relation is a table, it is always updatable */
    if (rel->rd_rel->relkind == RELKIND_RELATION ||
        rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
@@ -2740,11 +2757,15 @@ relation_is_updatable(Oid reloid,
                base_rte->relkind != RELKIND_PARTITIONED_TABLE)
            {
                baseoid = base_rte->relid;
+               outer_reloids = lcons_oid(RelationGetRelid(rel),
+                                         outer_reloids);
                include_cols = adjust_view_column_set(updatable_cols,
                                                      viewquery->targetList);
                auto_events &= relation_is_updatable(baseoid,
+                                                    outer_reloids,
                                                     include_triggers,
                                                     include_cols);
+               outer_reloids = list_delete_first(outer_reloids);
            }
            events |= auto_events;
        }

diff --git a/src/backend/utils/adt/misc.c b/src/backend/utils/adt/misc.c
index 62341b84d1c4566a7698ee929e45a189114f3bda..8700810ba3cb9038eb0d3cab94327d8daeb615de 100644 (file)
--- a/src/backend/utils/adt/misc.c
+++ b/src/backend/utils/adt/misc.c
@@ -681,7 +681,7 @@ pg_relation_is_updatable(PG_FUNCTION_ARGS)
    Oid         reloid = PG_GETARG_OID(0);
    bool        include_triggers = PG_GETARG_BOOL(1);
 
-   PG_RETURN_INT32(relation_is_updatable(reloid, include_triggers, NULL));
+   PG_RETURN_INT32(relation_is_updatable(reloid, NIL, include_triggers, NULL));
 }
 
 /*
@@ -705,7 +705,7 @@ pg_column_is_updatable(PG_FUNCTION_ARGS)
    if (attnum <= 0)
        PG_RETURN_BOOL(false);
 
-   events = relation_is_updatable(reloid, include_triggers,
+   events = relation_is_updatable(reloid, NIL, include_triggers,
                                   bms_make_singleton(col));
 
    /* We require both updatability and deletability of the relation */

diff --git a/src/include/rewrite/rewriteHandler.h b/src/include/rewrite/rewriteHandler.h
index 86ae571eb1a16f4c867054c1e5d6917221820c10..7f2fbccb77d42d12c5d6450d5ed4e5ea315d7d14 100644 (file)
--- a/src/include/rewrite/rewriteHandler.h
+++ b/src/include/rewrite/rewriteHandler.h
@@ -30,6 +30,7 @@ extern Query *get_view_query(Relation view);
 extern const char *view_query_is_auto_updatable(Query *viewquery,
                             bool check_cols);
 extern int relation_is_updatable(Oid reloid,
+                     List *outer_reloids,
                      bool include_triggers,
                      Bitmapset *include_cols);