mutt: Prevent null pointer exception for h->ai_canonname

[Brendan Cully]

changeset: 6940:943b281abfbb
user:      Athanasios Douitsis <aduit...@gmail.com>
date:      Sat Feb 18 21:30:27 2017 +0000
link:      http://dev.mutt.org/hg/mutt/rev/943b281abfbb

Prevent null pointer exception for h->ai_canonname

The getaddrinfo call in line 54 sets &h to a struct addrinfo. If a
canonical name cannot be found for the node argument of getaddrinfo,
h->ai_canonname is set to NULL. In that case, the strchr call in line
58 can lead to segfault. This behavior was observed on a macos sierra
while the hostname was 192.168.1.3 (unfortunately this happens quite
often in macos).

The fix is simple, just check h->ai_canonname for the NULL value.

diffs (12 lines):

diff -r 9b7780b48f47 -r 943b281abfbb getdomain.c
--- a/getdomain.c       Fri Feb 17 20:02:46 2017 -0800
+++ b/getdomain.c       Sat Feb 18 21:30:27 2017 +0000
@@ -55,7 +55,7 @@
     ret = -1;
   else
   {
-    if (!(p = strchr(h->ai_canonname, '.')))
+    if (!h->ai_canonname || !(p = strchr(h->ai_canonname, '.')))
       ret = -1;
     else
     {