Make LOAD of an already-loaded library into a no-op, instead of attempting

to unload and re-load the library.

The difficulty with unloading a library is that we haven't defined safe
protocols for doing so.  In particular, there's no safe mechanism for
getting out of a "hook" function pointer unless libraries are unloaded
in reverse order of loading.  And there's no mechanism at all for undefining
a custom GUC variable, so GUC would be left with a pointer to an old value
that might or might not still be valid, and very possibly wouldn't be in
the same place anymore.

While the unload and reload behavior had some usefulness in easing
development of new loadable libraries, it's of no use whatever to normal
users, so just disabling it isn't giving up that much.  Someday we might
care to expend the effort to develop safe unload protocols; but even if
we did, there'd be little certainty that every third-party loadable module
was following them, so some security restrictions would still be needed.

Back-patch to 8.2; before that, LOAD was superuser-only anyway.

Security: unprivileged users could crash backend.  CVE not assigned yet

diff --git a/doc/src/sgml/ref/create_function.sgml b/doc/src/sgml/ref/create_function.sgml
index ca9eca5138d98b06972fa6a27d3b2ea88138263c..5ebf170bdb6c188ca02637ef614ed5c46d208357 100644 (file)
--- a/doc/src/sgml/ref/create_function.sgml
+++ b/doc/src/sgml/ref/create_function.sgml
@@ -1,5 +1,5 @@
 
 
 
@@ -528,8 +528,7 @@ CREATE FUNCTION foo(int, int default 42) ...
     When repeated CREATE FUNCTION calls refer to
     the same object file, the file is only loaded once per session.
     To unload and
-    reload the file (perhaps during development), use the 
-    linkend="sql-load" endterm="sql-load-title"> command.
+    reload the file (perhaps during development), start a new session.
    
 
    


diff --git a/doc/src/sgml/ref/load.sgml b/doc/src/sgml/ref/load.sgml

index fca434096bc0e3e83108e556759f430a374b39f0..64237b09f5ac0f224d72741ae80fc57d992448a3 100644 (file)

--- a/doc/src/sgml/ref/load.sgml
+++ b/doc/src/sgml/ref/load.sgml
@@ -1,5 +1,5 @@
 
 
 
@@ -11,7 +11,7 @@ $PostgreSQL: pgsql/doc/src/sgml/ref/load.sgml,v 1.25 2008/11/14 10:22:47 petere
 
  
   LOAD
-  load or reload a shared library file
+  load a shared library file
  
 
  
@@ -29,13 +29,12 @@ LOAD 'filename'
 
   
    This command loads a shared library file into the PostgreSQL
-   server's address space.  If the file had been loaded previously,
-   it is first unloaded.  This command is primarily useful to unload
-   and reload a shared library file that has been changed since the
-   server first loaded it.  To make use of the shared library,
-   function(s) in it need to be declared using the 
-   linkend="sql-createfunction" endterm="sql-createfunction-title">
-   command.
+   server's address space.  If the file has been loaded already,
+   the command does nothing.  Shared library files that contain C functions
+   are automatically loaded whenever one of their functions is called.
+   Therefore, an explicit LOAD is usually only needed to
+   load a library that modifies the server's behavior through hooks
+   rather than providing a set of functions.
   
 
   


diff --git a/doc/src/sgml/xfunc.sgml b/doc/src/sgml/xfunc.sgml

index bb4fd68bb460da0e83c3dc45d69725a586ce2e98..6d85d2d262908850f2544ea11f732e35eb1a1d25 100644 (file)

--- a/doc/src/sgml/xfunc.sgml
+++ b/doc/src/sgml/xfunc.sgml
@@ -1,4 +1,4 @@
-
+
 
  
   User-Defined Functions
@@ -1481,9 +1481,7 @@ PG_MODULE_MAGIC;
     file is retained in memory.  Future calls in the same session to
     the function(s) in that file will only incur the small overhead of
     a symbol table lookup.  If you need to force a reload of an object
-    file, for example after recompiling it, use the 
-    linkend="sql-load" endterm="sql-load-title"> command or begin a
-    fresh session.
+    file, for example after recompiling it, begin a fresh session.
    
 
    
@@ -1509,8 +1507,8 @@ PG_MODULE_MAGIC;
     unloading the file.  Likewise, the function receives no parameters and
     should return void.  Note that _PG_fini will only be called
     during an unload of the file, not during process termination.
-    (Presently, an unload only happens in the context of re-loading
-    the file due to an explicit LOAD command.)
+    (Presently, unloads are disabled and will never occur, but this may
+    change in the future.)
    
 
   


diff --git a/src/backend/utils/fmgr/dfmgr.c b/src/backend/utils/fmgr/dfmgr.c

index 8b819df279c8cd0bf0009ee6fdbb745d4203630c..ef728dc3e8500aadebc10d4fafb031b2ac51a865 100644 (file)

--- a/src/backend/utils/fmgr/dfmgr.c
+++ b/src/backend/utils/fmgr/dfmgr.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/backend/utils/fmgr/dfmgr.c,v 1.99 2009/06/11 14:49:05 momjian Exp $
+ *   $PostgreSQL: pgsql/src/backend/utils/fmgr/dfmgr.c,v 1.100 2009/09/03 22:11:07 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -385,10 +385,17 @@ incompatible_module_error(const char *libname,
  * Unload the specified dynamic-link library file, if it is loaded.
  *
  * Note: libname is expected to be an exact name for the library file.
+ *
+ * XXX for the moment, this is disabled, resulting in LOAD of an already-loaded
+ * library always being a no-op.  We might re-enable it someday if we can
+ * convince ourselves we have safe protocols for un-hooking from hook function
+ * pointers, releasing custom GUC variables, and perhaps other things that
+ * are definitely unsafe currently.
  */
 static void
 internal_unload_library(const char *libname)
 {
+#ifdef NOT_USED
    DynamicFileList *file_scanner,
               *prv,
               *nxt;
@@ -436,6 +443,7 @@ internal_unload_library(const char *libname)
        else
            prv = file_scanner;
    }
+#endif /* NOT_USED */
 }
 
 static bool




This is the main PostgreSQL git repository.
RSS
Atom

diff --git a/doc/src/sgml/ref/load.sgml b/doc/src/sgml/ref/load.sgml
index fca434096bc0e3e83108e556759f430a374b39f0..64237b09f5ac0f224d72741ae80fc57d992448a3 100644 (file)
--- a/doc/src/sgml/ref/load.sgml
+++ b/doc/src/sgml/ref/load.sgml
@@ -1,5 +1,5 @@
 
 
 
@@ -11,7 +11,7 @@ $PostgreSQL: pgsql/doc/src/sgml/ref/load.sgml,v 1.25 2008/11/14 10:22:47 petere
 
  
   LOAD
-  load or reload a shared library file
+  load a shared library file
  
 
  
@@ -29,13 +29,12 @@ LOAD 'filename'
 
   
    This command loads a shared library file into the PostgreSQL
-   server's address space.  If the file had been loaded previously,
-   it is first unloaded.  This command is primarily useful to unload
-   and reload a shared library file that has been changed since the
-   server first loaded it.  To make use of the shared library,
-   function(s) in it need to be declared using the 
-   linkend="sql-createfunction" endterm="sql-createfunction-title">
-   command.
+   server's address space.  If the file has been loaded already,
+   the command does nothing.  Shared library files that contain C functions
+   are automatically loaded whenever one of their functions is called.
+   Therefore, an explicit LOAD is usually only needed to
+   load a library that modifies the server's behavior through hooks
+   rather than providing a set of functions.
   
 
   


diff --git a/doc/src/sgml/xfunc.sgml b/doc/src/sgml/xfunc.sgml

index bb4fd68bb460da0e83c3dc45d69725a586ce2e98..6d85d2d262908850f2544ea11f732e35eb1a1d25 100644 (file)

--- a/doc/src/sgml/xfunc.sgml
+++ b/doc/src/sgml/xfunc.sgml
@@ -1,4 +1,4 @@
-
+
 
  
   User-Defined Functions
@@ -1481,9 +1481,7 @@ PG_MODULE_MAGIC;
     file is retained in memory.  Future calls in the same session to
     the function(s) in that file will only incur the small overhead of
     a symbol table lookup.  If you need to force a reload of an object
-    file, for example after recompiling it, use the 
-    linkend="sql-load" endterm="sql-load-title"> command or begin a
-    fresh session.
+    file, for example after recompiling it, begin a fresh session.
    
 
    
@@ -1509,8 +1507,8 @@ PG_MODULE_MAGIC;
     unloading the file.  Likewise, the function receives no parameters and
     should return void.  Note that _PG_fini will only be called
     during an unload of the file, not during process termination.
-    (Presently, an unload only happens in the context of re-loading
-    the file due to an explicit LOAD command.)
+    (Presently, unloads are disabled and will never occur, but this may
+    change in the future.)
    
 
   


diff --git a/src/backend/utils/fmgr/dfmgr.c b/src/backend/utils/fmgr/dfmgr.c

index 8b819df279c8cd0bf0009ee6fdbb745d4203630c..ef728dc3e8500aadebc10d4fafb031b2ac51a865 100644 (file)

--- a/src/backend/utils/fmgr/dfmgr.c
+++ b/src/backend/utils/fmgr/dfmgr.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/backend/utils/fmgr/dfmgr.c,v 1.99 2009/06/11 14:49:05 momjian Exp $
+ *   $PostgreSQL: pgsql/src/backend/utils/fmgr/dfmgr.c,v 1.100 2009/09/03 22:11:07 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -385,10 +385,17 @@ incompatible_module_error(const char *libname,
  * Unload the specified dynamic-link library file, if it is loaded.
  *
  * Note: libname is expected to be an exact name for the library file.
+ *
+ * XXX for the moment, this is disabled, resulting in LOAD of an already-loaded
+ * library always being a no-op.  We might re-enable it someday if we can
+ * convince ourselves we have safe protocols for un-hooking from hook function
+ * pointers, releasing custom GUC variables, and perhaps other things that
+ * are definitely unsafe currently.
  */
 static void
 internal_unload_library(const char *libname)
 {
+#ifdef NOT_USED
    DynamicFileList *file_scanner,
               *prv,
               *nxt;
@@ -436,6 +443,7 @@ internal_unload_library(const char *libname)
        else
            prv = file_scanner;
    }
+#endif /* NOT_USED */
 }
 
 static bool

diff --git a/doc/src/sgml/xfunc.sgml b/doc/src/sgml/xfunc.sgml
index bb4fd68bb460da0e83c3dc45d69725a586ce2e98..6d85d2d262908850f2544ea11f732e35eb1a1d25 100644 (file)
--- a/doc/src/sgml/xfunc.sgml
+++ b/doc/src/sgml/xfunc.sgml
@@ -1,4 +1,4 @@
-
+
 
  
   User-Defined Functions
@@ -1481,9 +1481,7 @@ PG_MODULE_MAGIC;
     file is retained in memory.  Future calls in the same session to
     the function(s) in that file will only incur the small overhead of
     a symbol table lookup.  If you need to force a reload of an object
-    file, for example after recompiling it, use the 
-    linkend="sql-load" endterm="sql-load-title"> command or begin a
-    fresh session.
+    file, for example after recompiling it, begin a fresh session.
    
 
    
@@ -1509,8 +1507,8 @@ PG_MODULE_MAGIC;
     unloading the file.  Likewise, the function receives no parameters and
     should return void.  Note that _PG_fini will only be called
     during an unload of the file, not during process termination.
-    (Presently, an unload only happens in the context of re-loading
-    the file due to an explicit LOAD command.)
+    (Presently, unloads are disabled and will never occur, but this may
+    change in the future.)
    
 
   


diff --git a/src/backend/utils/fmgr/dfmgr.c b/src/backend/utils/fmgr/dfmgr.c

index 8b819df279c8cd0bf0009ee6fdbb745d4203630c..ef728dc3e8500aadebc10d4fafb031b2ac51a865 100644 (file)

--- a/src/backend/utils/fmgr/dfmgr.c
+++ b/src/backend/utils/fmgr/dfmgr.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/backend/utils/fmgr/dfmgr.c,v 1.99 2009/06/11 14:49:05 momjian Exp $
+ *   $PostgreSQL: pgsql/src/backend/utils/fmgr/dfmgr.c,v 1.100 2009/09/03 22:11:07 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -385,10 +385,17 @@ incompatible_module_error(const char *libname,
  * Unload the specified dynamic-link library file, if it is loaded.
  *
  * Note: libname is expected to be an exact name for the library file.
+ *
+ * XXX for the moment, this is disabled, resulting in LOAD of an already-loaded
+ * library always being a no-op.  We might re-enable it someday if we can
+ * convince ourselves we have safe protocols for un-hooking from hook function
+ * pointers, releasing custom GUC variables, and perhaps other things that
+ * are definitely unsafe currently.
  */
 static void
 internal_unload_library(const char *libname)
 {
+#ifdef NOT_USED
    DynamicFileList *file_scanner,
               *prv,
               *nxt;
@@ -436,6 +443,7 @@ internal_unload_library(const char *libname)
        else
            prv = file_scanner;
    }
+#endif /* NOT_USED */
 }
 
 static bool

diff --git a/src/backend/utils/fmgr/dfmgr.c b/src/backend/utils/fmgr/dfmgr.c
index 8b819df279c8cd0bf0009ee6fdbb745d4203630c..ef728dc3e8500aadebc10d4fafb031b2ac51a865 100644 (file)
--- a/src/backend/utils/fmgr/dfmgr.c
+++ b/src/backend/utils/fmgr/dfmgr.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/backend/utils/fmgr/dfmgr.c,v 1.99 2009/06/11 14:49:05 momjian Exp $
+ *   $PostgreSQL: pgsql/src/backend/utils/fmgr/dfmgr.c,v 1.100 2009/09/03 22:11:07 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -385,10 +385,17 @@ incompatible_module_error(const char *libname,
  * Unload the specified dynamic-link library file, if it is loaded.
  *
  * Note: libname is expected to be an exact name for the library file.
+ *
+ * XXX for the moment, this is disabled, resulting in LOAD of an already-loaded
+ * library always being a no-op.  We might re-enable it someday if we can
+ * convince ourselves we have safe protocols for un-hooking from hook function
+ * pointers, releasing custom GUC variables, and perhaps other things that
+ * are definitely unsafe currently.
  */
 static void
 internal_unload_library(const char *libname)
 {
+#ifdef NOT_USED
    DynamicFileList *file_scanner,
               *prv,
               *nxt;
@@ -436,6 +443,7 @@ internal_unload_library(const char *libname)
        else
            prv = file_scanner;
    }
+#endif /* NOT_USED */
 }
 
 static bool