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Commit602a9ef

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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 safeprotocols for doing so. In particular, there's no safe mechanism forgetting out of a "hook" function pointer unless libraries are unloadedin reverse order of loading. And there's no mechanism at all for undefininga custom GUC variable, so GUC would be left with a pointer to an old valuethat might or might not still be valid, and very possibly wouldn't be inthe same place anymore.While the unload and reload behavior had some usefulness in easingdevelopment of new loadable libraries, it's of no use whatever to normalusers, so just disabling it isn't giving up that much. Someday we mightcare to expend the effort to develop safe unload protocols; but even ifwe did, there'd be little certainty that every third-party loadable modulewas 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
1 parent187e5d8 commit602a9ef

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4 files changed

+23
-19
lines changed

4 files changed

+23
-19
lines changed

‎doc/src/sgml/ref/create_function.sgml

Lines changed: 2 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
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<!--
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$PostgreSQL: pgsql/doc/src/sgml/ref/create_function.sgml,v 1.84 2008/12/31 02:25:03 tgl Exp $
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$PostgreSQL: pgsql/doc/src/sgml/ref/create_function.sgml,v 1.85 2009/09/03 22:11:07 tgl Exp $
33
-->
44

55
<refentry id="SQL-CREATEFUNCTION">
@@ -528,8 +528,7 @@ CREATE FUNCTION foo(int, int default 42) ...
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When repeated <command>CREATE FUNCTION</command> calls refer to
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the same object file, the file is only loaded once per session.
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To unload and
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reload the file (perhaps during development), use the <xref
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linkend="sql-load" endterm="sql-load-title"> command.
531+
reload the file (perhaps during development), start a new session.
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</para>
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<para>

‎doc/src/sgml/ref/load.sgml

Lines changed: 8 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
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<!--
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$PostgreSQL: pgsql/doc/src/sgml/ref/load.sgml,v 1.25 2008/11/14 10:22:47 petere Exp $
2+
$PostgreSQL: pgsql/doc/src/sgml/ref/load.sgml,v 1.26 2009/09/0322:11:07 tgl Exp $
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-->
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<refentry id="SQL-LOAD">
@@ -11,7 +11,7 @@ $PostgreSQL: pgsql/doc/src/sgml/ref/load.sgml,v 1.25 2008/11/14 10:22:47 petere
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<refnamediv>
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<refname>LOAD</refname>
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<refpurpose>loador reloada shared library file</refpurpose>
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<refpurpose>load a shared library file</refpurpose>
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</refnamediv>
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<indexterm zone="sql-load">
@@ -29,13 +29,12 @@ LOAD '<replaceable class="PARAMETER">filename</replaceable>'
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<para>
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This command loads a shared library file into the <productname>PostgreSQL</>
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server's address space. If the file had been loaded previously,
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it is first unloaded. This command is primarily useful to unload
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and reload a shared library file that has been changed since the
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server first loaded it. To make use of the shared library,
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function(s) in it need to be declared using the <xref
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linkend="sql-createfunction" endterm="sql-createfunction-title">
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command.
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server's address space. If the file has been loaded already,
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the command does nothing. Shared library files that contain C functions
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are automatically loaded whenever one of their functions is called.
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Therefore, an explicit <command>LOAD</> is usually only needed to
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load a library that modifies the server's behavior through <quote>hooks</>
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rather than providing a set of functions.
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</para>
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<para>

‎doc/src/sgml/xfunc.sgml

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Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
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<!-- $PostgreSQL: pgsql/doc/src/sgml/xfunc.sgml,v 1.138 2009/05/27 01:18:06 tgl Exp $ -->
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<!-- $PostgreSQL: pgsql/doc/src/sgml/xfunc.sgml,v 1.139 2009/09/03 22:11:07 tgl Exp $ -->
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<sect1 id="xfunc">
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<title>User-Defined Functions</title>
@@ -1481,9 +1481,7 @@ PG_MODULE_MAGIC;
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file is retained in memory. Future calls in the same session to
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the function(s) in that file will only incur the small overhead of
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a symbol table lookup. If you need to force a reload of an object
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file, for example after recompiling it, use the <xref
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linkend="sql-load" endterm="sql-load-title"> command or begin a
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fresh session.
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file, for example after recompiling it, begin a fresh session.
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</para>
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<indexterm zone="xfunc-c-dynload">
@@ -1509,8 +1507,8 @@ PG_MODULE_MAGIC;
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unloading the file. Likewise, the function receives no parameters and
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should return void. Note that <function>_PG_fini</> will only be called
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during an unload of the file, not during process termination.
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(Presently,an unload only happens in the context of re-loading
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the file due to an explicit <command>LOAD</> command.)
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(Presently,unloads are disabled and will never occur, but this may
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change in the future.)
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</para>
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</sect2>

‎src/backend/utils/fmgr/dfmgr.c

Lines changed: 9 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/utils/fmgr/dfmgr.c,v 1.99 2009/06/11 14:49:05 momjian Exp $
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* $PostgreSQL: pgsql/src/backend/utils/fmgr/dfmgr.c,v 1.100 2009/09/03 22:11:07 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
@@ -385,10 +385,17 @@ incompatible_module_error(const char *libname,
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* Unload the specified dynamic-link library file, if it is loaded.
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*
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* Note: libname is expected to be an exact name for the library file.
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*
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* XXX for the moment, this is disabled, resulting in LOAD of an already-loaded
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* library always being a no-op. We might re-enable it someday if we can
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* convince ourselves we have safe protocols for un-hooking from hook function
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* pointers, releasing custom GUC variables, and perhaps other things that
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* are definitely unsafe currently.
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*/
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staticvoid
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internal_unload_library(constchar*libname)
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{
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#ifdefNOT_USED
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DynamicFileList*file_scanner,
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*prv,
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*nxt;
@@ -436,6 +443,7 @@ internal_unload_library(const char *libname)
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else
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prv=file_scanner;
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}
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#endif/* NOT_USED */
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}
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staticbool

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