From 5186f7625e5fc0e3ae85419099a75d6aa93d8351 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Thu, 21 Nov 2019 16:21:43 -0500 Subject: [PATCH] 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. --- src/backend/rewrite/rewriteHandler.c | 21 +++++++++++++++++++++ src/backend/utils/adt/misc.c | 4 ++-- src/include/rewrite/rewriteHandler.h | 1 + 3 files changed, 24 insertions(+), 2 deletions(-) diff --git a/src/backend/rewrite/rewriteHandler.c b/src/backend/rewrite/rewriteHandler.c index 5b047d16629..fb81217679f 100644 --- a/src/backend/rewrite/rewriteHandler.c +++ b/src/backend/rewrite/rewriteHandler.c @@ -27,6 +27,7 @@ #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" @@ -2619,6 +2620,11 @@ 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 @@ -2637,6 +2643,7 @@ view_cols_are_auto_updatable(Query *viewquery, */ int relation_is_updatable(Oid reloid, + List *outer_reloids, bool include_triggers, Bitmapset *include_cols) { @@ -2646,6 +2653,9 @@ 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); /* @@ -2657,6 +2667,13 @@ 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) @@ -2777,11 +2794,15 @@ 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 d330a88e3c1..e59b61ba6f2 100644 --- a/src/backend/utils/adt/misc.c +++ b/src/backend/utils/adt/misc.c @@ -510,7 +510,7 @@ 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)); } /* @@ -534,7 +534,7 @@ 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 c55fe81a0a3..77b2ffa9621 100644 --- 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);