[tor-bugs] #10169 [Tor]: Extend OOM handler to cover channels/connection buffers

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#10169: Extend OOM handler to cover channels/connection buffers
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     Reporter:  nickm   |      Owner:
         Type:  defect  |     Status:  needs_review
     Priority:  major   |  Milestone:  Tor: 0.2.5.x-final
    Component:  Tor     |    Version:
   Resolution:          |   Keywords:  tor-relay oom 024-backport
Actual Points:          |  Parent ID:
       Points:          |
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Comment (by sysrqb):

 Reviewed bug10169_024.

 total_bytes_allocated_in_chunks still has a DOCDOC in buffers.c

 I wonder if END_CIRC_REASON_RESOURCELIMIT can be used to perform a
 modified sniper-based oracle attack if there's another way to fill the
 remaining 10% when the 90% memory usage is reached.

 It might be useful to the relay operator if Tor says how many circuits
 remained alive after circuits_handle_oom runs, e.g. modify the log notice
 at the end of that function.

 {{{
   int n_circuits_alive = smartlist_len(circlist) - n_circuits_killed;
   log_notice(LD_GENERAL, "Removed "U64_FORMAT" bytes by killing %d "
                          "circuits, %d circuits remain alive.",
              U64_PRINTF_ARG(mem_recovered), n_circuits_killed,
              n_circuits_alive);
 }}}

 Maybe the comments for circuit_get_streams_max_data_age and
 marked_circuit_streams_free_bytes should notate that they are helpers for
 circuit_max_queued_data_age and marked_circuit_free_stream_bytes,
 respectively?

 Is it possible that when the stream buffers are "aggressively freed" using
 chunk_free_unchecked() they may not actually be freed, but prepended to a
 freelist and, as a result, less memory is actually freed in
 circuits_handle_oom() than is expected?

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/10169#comment:10>
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