inserted additional checks for null values, comments

fixed deadlocks

diff --git a/servers/slapd/back-ldbm/alias.c b/servers/slapd/back-ldbm/alias.c
index 75cd074db2c0ec112a4126c66b58441d6a97b941..d328cc8d17536b25354c9fa4e735f798ef0e83e2 100644 (file)
--- a/servers/slapd/back-ldbm/alias.c
+++ b/servers/slapd/back-ldbm/alias.c
@@ -21,17 +21,21 @@
 
 /*
  * given an alias object, dereference it to its end point.
- * entry returned has reader lock 
+ * Entry returned has reader lock or is NULL.  Starting entry is not released.
  */
 Entry *derefAlias_r ( Backend     *be,
                    Connection  *conn,
                    Operation   *op,
                    Entry       *e)
 {
+  struct ldbminfo *li = (struct ldbminfo *) be->be_private; /* to free cache entries */
   Attribute *a;
   int       depth;
   char      **pastAliases;
   char      *matched;
+  Entry     *origDN = e;
+
+  if (!e) return NULL;  /* be sure we have a starting entry */
 
   Debug( LDAP_DEBUG_TRACE, "<= checking for alias for dn %s\n", e->e_dn, 0, 0 );
 
@@ -55,7 +59,40 @@ Entry *derefAlias_r ( Backend     *be,
       Debug( LDAP_DEBUG_TRACE, "<= %s is an alias for %s\n", 
             e->e_dn, a->a_vals[0]->bv_val, 0 );
       newDN = ch_strdup (a->a_vals[0]->bv_val);
-      oldDN = ch_strdup (e->e_dn);
+      oldDN = ch_strdup (e->e_ndn);
+
+      /* 
+       * release past lock if not original
+       */
+      if ( (depth > 0) && e ) {
+          cache_return_entry_r(&li->li_cache, e);      
+      }
+
+      /* make sure new and old DN are not same to avoid loops */
+      dn_normalize_case (newDN);
+      if ( strcmp (newDN, oldDN) == 0 ) {
+       
+       Debug( LDAP_DEBUG_TRACE, 
+              "<= %s alias is same as current %s\n", 
+              oldDN, newDN, 0 );
+       send_ldap_result( conn, op, LDAP_ALIAS_PROBLEM, "",
+                         "Circular alias" );
+       free (newDN);
+       free (oldDN);
+       break;
+      }
+
+      /* make sure new and original are not same to avoid deadlocks */
+      if ( strcmp (newDN, origDN->e_ndn) == 0 ) {
+       Debug( LDAP_DEBUG_TRACE, 
+              "<= %s alias is same as original %s\n", 
+              oldDN, origDN->e_ndn, 0 );
+       send_ldap_result( conn, op, LDAP_ALIAS_PROBLEM, "",
+                         "Circular alias" );
+       free (newDN);
+       free (oldDN);
+       break;
+      }
 
       /*
        * ok, so what happens if there is an alias in the DN of a dereferenced
@@ -67,11 +104,15 @@ Entry *derefAlias_r ( Backend     *be,
        Debug( LDAP_DEBUG_TRACE, 
               "<= %s is a dangling alias to %s\n", 
               oldDN, newDN, 0 );
-       send_ldap_result( conn, op, LDAP_ALIAS_PROBLEM, "",
+       send_ldap_result( conn, op, LDAP_ALIAS_DEREF_PROBLEM, "",
                          "Dangling Alias" );
 
-                       if(matched != NULL) free(matched);
+       if (matched != NULL) free(matched);
+       free (newDN);
+       free (oldDN);
+       break;
       }
+
       free (newDN);
       free (oldDN);
     }
@@ -82,9 +123,10 @@ Entry *derefAlias_r ( Backend     *be,
        */
        Debug( LDAP_DEBUG_TRACE, 
               "<= %s has no data in aliasedobjectname attribute\n", 
-              e->e_dn, 0, 0 );
+              (e && e->e_dn) ? e->e_dn : "(null)", 0, 0 );
        send_ldap_result( conn, op, LDAP_ALIAS_PROBLEM, "",
                          "Alias missing aliasedobjectname" );
+       break;
     }
   }
 
@@ -93,9 +135,11 @@ Entry *derefAlias_r ( Backend     *be,
    */
   if ( depth >= be->be_maxDerefDepth ) {
     Debug( LDAP_DEBUG_TRACE, 
-          "<= %s exceeded maximum deref depth %d\n", 
-          e->e_dn, be->be_maxDerefDepth, 0 );
-    send_ldap_result( conn, op, LDAP_ALIAS_PROBLEM, "",
+          "<= deref(\"%s\") exceeded maximum deref depth (%d) at \"%s\"\n", 
+          origDN->e_dn ? origDN->e_dn : "(null)", 
+          be->be_maxDerefDepth, 
+          (e && e->e_ndn) ? e->e_ndn : "(null)");
+    send_ldap_result( conn, op, LDAP_ALIAS_DEREF_PROBLEM, "",
                        "Maximum alias dereference depth exceeded" );
   }
 
@@ -104,6 +148,17 @@ Entry *derefAlias_r ( Backend     *be,
 
 /*
  * given a DN fully deref it and return the real DN or original DN if it fails
+ * This involves finding the last matched part then reconstructing forward
+ * e.g. 
+ * ou=MyOU,o=MyAliasedOrg,c=MyCountry where o=MyAliasedOrg is an alias for o=MyOrg
+ * loop starts with newDN = ou=MyOU,o=MyAliasedOrg,c=MyCountry
+ *   dn2entry_r on newDN gives null entry and o=MyAliasedOrg,c=MyCountry matched
+ *   dn2entry_r on matched gives o=MyAliasedOrg,c=MyCountry entry
+ *   remainder is ou=MyOU
+ *   dereferencing o=MyAliasedOrg,c=MyCountry yields entry o=MyOrg,c=MyCountry
+ *   release lock on o=MyAliasedOrg,c=MyCountry entry
+ *   reconstructed dn is ou=MyOU,o=MyOrg,c=MyCountry
+ *   release lock on o=MyOrg,c=MyCountry entry
  */
 char *derefDN ( Backend     *be,
                 Connection  *conn,
@@ -119,6 +174,7 @@ char *derefDN ( Backend     *be,
   Entry        *eDeref;
   Entry         *eNew;
   
+  if (!dn) return NULL; 
 
   Debug( LDAP_DEBUG_TRACE, 
         "<= dereferencing dn: \"%s\"\n", 
@@ -134,7 +190,7 @@ char *derefDN ( Backend     *be,
     
     if ((matched != NULL) && *matched) {       
       char *submatch;
-      
+   
       /* 
        * make sure there actually is an entry for the matched part 
        */
@@ -157,6 +213,9 @@ char *derefDN ( Backend     *be,
          newDN = NULL;
          free (remainder);
          remainder = NULL;
+         
+         cache_return_entry_r(&li->li_cache, eMatched);
+         eMatched = NULL;
          break; /*  no associated entry, dont deref */
        }
        else {
@@ -166,13 +225,18 @@ char *derefDN ( Backend     *be,
          i = strcasecmp (matched, eNew->e_dn);
           /* free reader lock */
           cache_return_entry_r(&li->li_cache, eNew);
+
+         free (matched);
+         matched = NULL;
+
          if (! i) {
            /* newDN same as old so not an alias, no need to go further */
            free (newDN);
            newDN = NULL;
-           free (matched);
-           matched = NULL;
            free (remainder);
+
+           cache_return_entry_r(&li->li_cache, eMatched);
+           eMatched = NULL;
            break;
          }
 
@@ -186,12 +250,10 @@ char *derefDN ( Backend     *be,
          strcat (newDN, eMatched->e_dn);
          Debug( LDAP_DEBUG_TRACE, "<= expanded to %s\n", newDN, 0, 0 );
 
-         free (matched);
-         matched = NULL;
          free (remainder);
        }
-        /* free reader lock */
-        cache_return_entry_r(&li->li_cache, eMatched);
+       /* free reader lock */
+       cache_return_entry_r(&li->li_cache, eMatched);
       }
       else {
        if(submatch != NULL) free(submatch);
@@ -203,14 +265,18 @@ char *derefDN ( Backend     *be,
     }
   }
   
+  /* release lock if a match terminated the loop, there should be no
+   * outstanding locks at this point
+   */
   if(eMatched != NULL) {
     /* free reader lock */
     cache_return_entry_r(&li->li_cache, eMatched);
   }
 
   /*
-   * the final part of the DN might be an alias 
-   * so try to dereference it.
+   * the final part of the DN might be an alias so try to dereference it.
+   * e.g. if we had started with dn = o=MyAliasedOrg,c=MyCountry the dn would match
+   * and the above loop complete but we would still be left with an aliased DN.
    */
   if ( (eNew = dn2entry_r( be, newDN, &matched )) != NULL) {
     if ((eDeref = derefAlias_r( be, conn, op, eNew )) != NULL) {
@@ -222,15 +288,25 @@ char *derefDN ( Backend     *be,
     /* free reader lock */
     cache_return_entry_r(&li->li_cache, eNew);
   }
+  if (matched != NULL) free(matched);
   
   /*
    * warn if we exceeded the max depth as the resulting DN may not be dereferenced
    */
   if (depth >= be->be_maxDerefDepth) {
-    Debug( LDAP_DEBUG_TRACE, 
-          "<= max deref depth exceeded in derefDN for \"%s\", result \"%s\"\n", 
-          dn, newDN, 0 );
-    send_ldap_result( conn, op, LDAP_ALIAS_PROBLEM, "",
+    if (newDN) {
+      Debug( LDAP_DEBUG_TRACE, 
+            "<= max deref depth exceeded in derefDN for \"%s\", result \"%s\"\n", 
+            dn, newDN, 0 );
+      free (newDN);
+      newDN = NULL;
+    }
+    else {
+      Debug( LDAP_DEBUG_TRACE, 
+            "<= max deref depth exceeded in derefDN for \"%s\", result NULL\n", 
+            dn, 0, 0 );
+    }
+    send_ldap_result( conn, op, LDAP_ALIAS_DEREF_PROBLEM, "",
                      "Maximum alias dereference depth exceeded for base" );
   }
 
@@ -239,7 +315,6 @@ char *derefDN ( Backend     *be,
   }
   
   Debug( LDAP_DEBUG_TRACE, "<= returning deref DN of \"%s\"\n", newDN, 0, 0 ); 
-  if (matched != NULL) free(matched);
 
   return newDN;
 }