[tor-commits] [tor/master] Fix crash when changing node restrictions with DNS lookup in progress

[nickm at torproject.org]

commit 5aa45ed6af87efaec5d6d4a32e8acbc733be8c3d
Author: Nick Mathewson <nickm at torproject.org>
Date:   Wed Oct 19 23:14:05 2011 -0400

    Fix crash when changing node restrictions with DNS lookup in progress
    
    Fixes bug 4259, bugfix on 0.2.2.25-alpha.  Bugfix by "Tey'".
    
    Original message by submitter:
    
      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.
---
 changes/bug4259          |    4 ++++
 src/or/connection_edge.c |    5 ++++-
 2 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/changes/bug4259 b/changes/bug4259
new file mode 100644
index 0000000..bfccd3a
--- /dev/null
+++ b/changes/bug4259
@@ -0,0 +1,4 @@
+  o Major bugfixes:
+    - Fix a crash bug when changing node restrictions while a DNS lookup
+      is in-progress. Fixes bug 4259; bugfix on 0.2.2.25-alpha. Bugfix
+      by "Tey'".
diff --git a/src/or/connection_edge.c b/src/or/connection_edge.c
index 6a69609..4763bf5 100644
--- a/src/or/connection_edge.c
+++ b/src/or/connection_edge.c
@@ -831,7 +831,10 @@ addressmap_clear_excluded_trackexithosts(or_options_t *options)
     char *nodename;
     routerinfo_t *ri; /* XXX023 Use node_t. */
 
-    if (strcmpend(target, ".exit")) {
+    if (!target) {
+      /* DNS resolving in progress */
+      continue;
+    } else if (strcmpend(target, ".exit")) {
       /* Not a .exit mapping */
       continue;
     } else if (ent->source != ADDRMAPSRC_TRACKEXIT) {