Fix portalmem.c to avoid keeping a dangling pointer to a cached plan list

after it's released its reference count for the cached plan.  There are
code paths that might try to examine the plan list before noticing that
the portal is already in aborted state.  Report and diagnosis by Tatsuo
Ishii, though this isn't exactly his proposed patch.

diff --git a/src/backend/utils/mmgr/portalmem.c b/src/backend/utils/mmgr/portalmem.c
index 217c6b1234b6e3c8cce637b8408d6c8a69d0eba7..7fe28ca15fa6ea6bf705778fee4f963f82aceef3 100644 (file)
--- a/src/backend/utils/mmgr/portalmem.c
+++ b/src/backend/utils/mmgr/portalmem.c
@@ -12,7 +12,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/utils/mmgr/portalmem.c,v 1.106.2.2 2009/12/29 17:41:18 heikki Exp $
+ *       $PostgreSQL: pgsql/src/backend/utils/mmgr/portalmem.c,v 1.106.2.3 2010/01/18 02:30:37 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -324,6 +324,13 @@ PortalReleaseCachedPlan(Portal portal)
        {
                ReleaseCachedPlan(portal->cplan, false);
                portal->cplan = NULL;
+
+               /*
+                * We must also clear portal->stmts which is now a dangling
+                * reference to the cached plan's plan list.  This protects any
+                * code that might try to examine the Portal later.
+                */
+               portal->stmts = NIL;
        }
 }
 
@@ -385,8 +392,7 @@ PortalDrop(Portal portal, bool isTopCommit)
                (*portal->cleanup) (portal);
 
        /* drop cached plan reference, if any */
-       if (portal->cplan)
-               PortalReleaseCachedPlan(portal);
+       PortalReleaseCachedPlan(portal);
 
        /*
         * Release any resources still attached to the portal.  There are several
@@ -519,8 +525,7 @@ CommitHoldablePortals(void)
                        PersistHoldablePortal(portal);
 
                        /* drop cached plan reference, if any */
-                       if (portal->cplan)
-                               PortalReleaseCachedPlan(portal);
+                       PortalReleaseCachedPlan(portal);
 
                        /*
                         * Any resources belonging to the portal will be released in the
@@ -670,8 +675,7 @@ AtAbort_Portals(void)
                }
 
                /* drop cached plan reference, if any */
-               if (portal->cplan)
-                       PortalReleaseCachedPlan(portal);
+               PortalReleaseCachedPlan(portal);
 
                /*
                 * Any resources belonging to the portal will be released in the
@@ -813,8 +817,7 @@ AtSubAbort_Portals(SubTransactionId mySubid,
                        }
 
                        /* drop cached plan reference, if any */
-                       if (portal->cplan)
-                               PortalReleaseCachedPlan(portal);
+                       PortalReleaseCachedPlan(portal);
 
                        /*
                         * Any resources belonging to the portal will be released in the