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 8efcc97d1e2da05fc644fd9e516a5a4b3c33b505..1012453bae0e05625959c69e495985ba71ebb2dc 100644 (file)
--- a/src/backend/rewrite/rewriteHandler.c
+++ b/src/backend/rewrite/rewriteHandler.c
@@ -17,6 +17,7 @@
 #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"
@@ -2517,6 +2518,11 @@ 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
@@ -2535,6 +2541,7 @@ view_cols_are_auto_updatable(Query *viewquery,
  */
 int
 relation_is_updatable(Oid reloid,
+                                         List *outer_reloids,
                                          bool include_triggers,
                                          Bitmapset *include_cols)
 {
@@ -2544,6 +2551,9 @@ 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);
 
        /*
@@ -2555,6 +2565,13 @@ 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)
        {
@@ -2673,11 +2690,15 @@ relation_is_updatable(Oid reloid,
                        if (base_rte->relkind != RELKIND_RELATION)
                        {
                                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 3ef6e43c4d01d7b17f38d9f72765f2dfadfde975..4ac8183f36af56e307844d46b9a87dd5e8602393 100644 (file)
--- a/src/backend/utils/adt/misc.c
+++ b/src/backend/utils/adt/misc.c
@@ -566,7 +566,7 @@ 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));
 }
 
 /*
@@ -590,7 +590,7 @@ 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 c9a2d25f90e300f9fde50c0e8551f545c5d30730..ab23691063cdcb3d7f4b39ad2748495707d59e2d 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);