[tor-bugs] #29122 [Core Tor/Tor]: Intermittent test failure in circuitpadding/circuitpadding_wronghop

[Tor Bug Tracker & Wiki]

#29122: Intermittent test failure in circuitpadding/circuitpadding_wronghop
--------------------------+------------------------------------
 Reporter:  nickm         |          Owner:  (none)
     Type:  defect        |         Status:  reopened
 Priority:  Medium        |      Milestone:  Tor: 0.4.0.x-final
Component:  Core Tor/Tor  |        Version:
 Severity:  Normal        |     Resolution:
 Keywords:                |  Actual Points:
Parent ID:                |         Points:
 Reviewer:  nickm         |        Sponsor:
--------------------------+------------------------------------

Comment (by asn):

 OK, while this is not the same bug as the original bug of this ticket,
 let's use the same ticket for it (the original bug was in
 `circuitpadding_wronghop`, the teor one is in `circuitsetup_machine`).

 So, I discussed this with mikeperry in brussels and we figured out what's
 the issue. The issue is that `circuitpadding_circuitsetup_machine` uses a
 2-bin histogram, and the fact that it only has 2-bins causes undefined
 behavior since the spec has conflicting rules about how 2-bin histograms
 work. In particular, the current spec causes UB for 1-bin 2-bin and 3-bin
 histograms, because of the way the bin edges are calculated automatically.

 The long-term fix here is to do #29298 which allows the histogram designer
 to specify the bin edges themselves, but we will do this in 041 since it's
 a non-trivial fix. The short-term fix here is probably to disable this
 unittest until the 041 fix comes in. Mike, do you agree?

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/29122#comment:13>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online