[tor-bugs] #7164 [Tor]: microdesc.c:378: Bug: microdesc_free() called, but md was still referenced 1 node(s); held_by_nodes == 1

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#7164: microdesc.c:378: Bug: microdesc_free() called, but md was still referenced
1 node(s); held_by_nodes == 1
------------------------+-------------------------------------
     Reporter:  jaj123  |      Owner:
         Type:  defect  |     Status:  needs_review
     Priority:  major   |  Milestone:  Tor: 0.2.5.x-final
    Component:  Tor     |    Version:  Tor: 0.2.4.19
   Resolution:          |   Keywords:  tor-client 024-backport
Actual Points:          |  Parent ID:
       Points:          |
------------------------+-------------------------------------
Changes (by nickm):

 * status:  new => needs_review
 * milestone:  Tor: 0.2.4.x-final => Tor: 0.2.5.x-final


Comment:

 The line number suggests that this is happening in
 microdesc_cache_clean():

 {{{
   for (mdp = HT_START(microdesc_map, &cache->map); mdp != NULL; ) {
     if ((*mdp)->last_listed < cutoff) {
       ++dropped;
       victim = *mdp;
       mdp = HT_NEXT_RMV(microdesc_map, &cache->map, mdp);
       victim->held_in_map = 0;
       bytes_dropped += victim->bodylen;
       microdesc_free(victim);
     } else {
       ++kept;
       mdp = HT_NEXT(microdesc_map, &cache->map, mdp);
     }
   }
 }}}

 So, there's a microdesc that is (probably) held by a node, but its last-
 listed is more than one week ago.  Interesting!

 In theory:
   * A node should not exist unless it has a routerstatus or a routerinfo.
   * A node should not have a microdescriptor unless it has a routerstatus.
   * Whenever a networkstatus is loaded, we should be updating the
 last_seen field of the microdescriptors.

 So something has gone wrong with the theory.

 I'm not too sure what -- if somebody has ideas, that would be great.  I've
 tried to write an improved diagnostic branch.  Please review
 "bug7164_diagnose_harder" in my public repository.  It's more logs, not a
 fix.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/7164#comment:30>
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