dnsmasq/dnsmasq-2.77-underflow.patch

From 77c7cabbeab1fbe1f7296f33762771f208586e59 Mon Sep 17 00:00:00 2001
From: Doran Moppert <dmoppert@redhat.com>
Date: Tue, 26 Sep 2017 14:48:20 +0930
Subject: [PATCH] google patch hand-applied

---
 src/edns0.c   | 10 +++++-----
 src/forward.c |  4 ++++
 src/rfc1035.c |  3 +++
 3 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/src/edns0.c b/src/edns0.c
index 7bd26b8..7f96414 100644
--- a/src/edns0.c
+++ b/src/edns0.c
@@ -212,11 +212,11 @@ size_t add_pseudoheader(struct dns_header *header, size_t plen, unsigned char *l
       /* Copy back any options */
       if (buff)
 	{
-          if (p + rdlen > limit)
-          {
-            free(buff);
-            return plen; /* Too big */
-          }
+	  if (p + rdlen > limit)
+	  {
+	    free(buff);
+	    return plen; /* Too big */
+	  }
 	  memcpy(p, buff, rdlen);
 	  free(buff);
 	  p += rdlen;
diff --git a/src/forward.c b/src/forward.c
index 3d638e4..e254e35 100644
--- a/src/forward.c
+++ b/src/forward.c
@@ -1558,6 +1558,10 @@ void receive_query(struct listener *listen, time_t now)
 	udp_size = PACKETSZ; /* Sanity check - can't reduce below default. RFC 6891 6.2.3 */
     }
 
+  // Make sure the udp size is not smaller than the incoming message so that we
+  // do not underflow
+  if (udp_size < n) udp_size = n;
+
 #ifdef HAVE_CONNTRACK
 #ifdef HAVE_AUTH
   if (!auth_dns || local_auth)
diff --git a/src/rfc1035.c b/src/rfc1035.c
index 6fc4f26..66fa00c 100644
--- a/src/rfc1035.c
+++ b/src/rfc1035.c
@@ -1396,6 +1396,9 @@ size_t answer_request(struct dns_header *header, char *limit, size_t qlen,
   size_t len;
   int rd_bit = (header->hb3 & HB3_RD);
 
+  // Make sure we do not underflow here too.
+  if (qlen > (limit - ((char *)header))) return 0;
+
   /* never answer queries with RD unset, to avoid cache snooping. */
   if (ntohs(header->ancount) != 0 ||
       ntohs(header->nscount) != 0 ||
-- 
2.31.1