Fix possible SEGV when no servers defined.

If there exists a --address=/<domain>/  or --server=/<domain>/#
configuration but no upstream server config unqualified by
domain then when a query which doesnt match the domain is
recieved it will use the qualfied server config and in the process
possibly make an out-of-bounds memory access.

Thanks to Daniel Danzberger for spotting the bug.

2 files changed, 14 insertions, 2 deletions

diff --git a/CHANGELOG b/CHANGELOG
index de9c5e0..3af20cf 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,14 @@
+version 2.90
+	Fix reversion in --rev-server introduced in 2.88 which
+	caused breakage if the prefix length is not exactly divisible
+	by 8 (IPv4) or 4 (IPv6).
+
+	Fix possible SEGV when there server(s) for a particular
+	domain are configured, but no server which is not qualified
+	for a particular domain. Thanks to Daniel Danzberger for
+	spotting this bug.
+	
+
 version 2.89
         Fix bug introduced in 2.88 (commit fe91134b) which can result
 	in corruption of the DNS cache internal data structures and
diff --git a/src/domain-match.c b/src/domain-match.c
index fe8e25a..9cc51e6 100644
--- a/src/domain-match.c
+++ b/src/domain-match.c
@@ -253,9 +253,10 @@ int lookup_domain(char *domain, int flags, int *lowout, int *highout)
   if (highout)
     *highout = nhigh;
 
-  if (nlow == nhigh)
+  /* qlen == -1 when we failed to match even an empty query, if there are no default servers. */
+  if (nlow == nhigh || qlen == -1)
     return 0;
-
+  
   return 1;
 }