Re: [tor-bugs] #15901 [Tor]: apparent memory corruption -- very difficult to isolate

["Tor Bug Tracker & Wiki" <blackhole@xxxxxxxxxxxxxx>]

#15901: apparent memory corruption -- very difficult to isolate
---------------------------+--------------------------------
     Reporter:  starlight  |      Owner:
         Type:  defect     |     Status:  new
     Priority:  critical   |  Milestone:  Tor: 0.2.7.x-final
    Component:  Tor        |    Version:  Tor: 0.2.6.10
   Resolution:             |   Keywords:
Actual Points:             |  Parent ID:
       Points:             |
---------------------------+--------------------------------

Comment (by someone_else):

 Actually looking at the source code, it doesn't look like random memory
 corruption or a threading issue. The consensus document signatures are
 checked as soon as the new document is downloaded:

 src/or/directory.c::connection_dir_client_reached_eof(dir_connection_t
 *conn)
 {{{
 ...
 // networkstatus_set_current_consensus performs signature check
 if ((r=networkstatus_set_current_consensus(body, flavname, 0))<0) {
 ...
 }}}
 Looking at your log files, you are downloading the consensus from multiple
 different directories and it gets corrupted the same way each time. In
 your 'event04_messages.txt' the same descriptor is corrupted. This points
 to a potential gzip or zlib decoding issue (maybe the decompression code
 is getting miscompiled).

 The best chance of tracking this down is probably to instrument the
 function mentioned above and save both the compressed and uncompressed
 versions of the consensus to disk.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/15901#comment:25>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online
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