[tor-bugs] #4259 [Tor Client]: [PATCH] Tor crashes when nodes restrictions are changed at runtime

[Tor Bug Tracker & Wiki]

#4259: [PATCH] Tor crashes when nodes restrictions are changed at runtime
------------------------+---------------------------------------------------
 Reporter:  Tey'        |          Owner:               
     Type:  defect      |         Status:  new          
 Priority:  normal      |      Milestone:               
Component:  Tor Client  |        Version:  Tor: 0.2.2.32
 Keywords:              |         Parent:               
   Points:              |   Actualpoints:               
------------------------+---------------------------------------------------
 Hi,

 Changing nodes restrictions using a controller while Tor is doing DNS
 resolution could makes Tor crashes (on WinXP at least). The problem can be
 repeated by trying to reach a non-existent domain using Tor:
   curl --socks4a 127.0.0.1:9050 inexistantdomain.ext
 .. and changing the ExitNodes parameter through the control port before
 Tor returns a DNS resolution error (of course, the following command won't
 work directly if the control port is password protected):
   echo SETCONF ExitNodes=TinyTurtle | nc -v 127.0.0.1 9051

 Using a non-existent domain is needed to repeat the issue so that Tor
 takes a few seconds for resolving the domain (which allows us to change
 the configuration). Tor will crash while processing the configuration
 change.

 The bug is located in the addressmap_clear_excluded_trackexithosts method
 which iterates over the entries of the addresses map in order to check
 whether the changes made to the configuration will impact those entries.
 When a DNS resolving is in progress, the new_adress field of the
 associated entry will be set to NULL. The method doesn't expect this field
 to be NULL, hence the crash.

 I attached a patch that fixes the problem.

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/4259>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online