Taken from http://www.linuxfromscratch.org/lfs/view/development/chapter06/glibc.html

--- resolv/nss_dns/dns-host.c	2015-02-06 07:40:18.000000000 +0100
+++ resolv/nss_dns/dns-host.c	2015-04-25 17:38:58.365119958 +0200
@@ -615,7 +615,8 @@
   int have_to_map = 0;
   uintptr_t pad = -(uintptr_t) buffer % __alignof__ (struct host_data);
   buffer += pad;
-  if (__glibc_unlikely (buflen < sizeof (struct host_data) + pad))
+  buflen = buflen > pad ? buflen - pad : 0;
+  if (__glibc_unlikely (buflen < sizeof (struct host_data)))
     {
       /* The buffer is too small.  */
     too_small:
