Config file statement ordering (Was: (ITS#4848) Another slapd startup segfault)

[Pierangelo Masarati <ando@sys-net.it>]

ando@sys-net.it wrote:

> The above had nothing to do with your problem.  Your problem is related
> to the fact that you intermixed overlay and database configuration
> statements, so the idletimeout statement after the accesslog overlay
> instantiation was causing invalid memory write (beyond the private data
> of the accesslog overlay instead of in the private data of the bdb
> database) resulting in heap corruption.
> 
> Maybe it hasn't been stressed enough, but the order of directives is:


I believe the problem is here:

=========================================================================
diff -u -r1.341.2.25 config.c
--- servers/slapd/config.c      8 Feb 2007 12:31:24 -0000       1.341.2.25
+++ servers/slapd/config.c      24 Feb 2007 13:29:42 -0000
@@ -308,13 +308,28 @@
                return(0);
        }
        if(arg_type & ARG_OFFSET) {
-               if (c->be && (!overlay_is_over(c->be) ||
-                       ((slap_overinfo *)c->be->bd_info)->oi_orig ==
c->bi))
-                       ptr = c->be->be_private;
-               else if (c->bi)
+               if ( c->be ) {
+                       if (!overlay_is_over(c->be) ||
+                               ((slap_overinfo
*)c->be->bd_info)->oi_orig == c->bi)
+                       {
+                               ptr = c->be->be_private;
+
+                       } else {
+                               snprintf( c->msg, sizeof( c->msg ),
+                                       "<%s> statement outside scope "
+                                       "(after overlay?)",
+                                       c->argv[0] );
+                               Debug(LDAP_DEBUG_CONFIG, "%s: %s!\n",
+                                       c->log, c->msg, 0);
+                               return(ARG_BAD_CONF);
+                       }
+
+               } else if ( c->bi ) {
                        ptr = c->bi->bi_private;
-               else {
-                       snprintf( c->msg, sizeof( c->msg ), "<%s> offset
is missing base pointer",
+
+               } else {
+                       snprintf( c->msg, sizeof( c->msg ),
+                               "<%s> offset is missing base pointer",
                                c->argv[0] );
                        Debug(LDAP_DEBUG_CONFIG, "%s: %s!\n",
                                c->log, c->msg, 0);
=========================================================================

that is, if both the database and the overlay allow back-config, there
are cases in which config_set_vals() can be called with (arg_type &
ARG_OFFSET) and the c->be points to the database's structure while c->bi
points to the overlay's structure, and the config statement refers to
the database although appearing after the overlay's instantiation.

This is Bad (TM) and should be avoided.  However, for example, I have
special needs in back-meta that require to allow overlay instantiation
__before__ the database configuration is complete (in that case, I need
an overlay to be instantiated before targets are defined, so that the
overlay can get per-target configuration parameters much like the
underlying database does).  This may defer introduction of back-config
support for back-meta.

Comments?



Ing. Pierangelo Masarati
OpenLDAP Core Team

SysNet s.n.c.
Via Dossi, 8 - 27100 Pavia - ITALIA
http://www.sys-net.it
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