Patch rediffed for 2.77 by Julien

From 51eadb692a5123b9838e5a68ecace3ac579a3a45 Mon Sep 17 00:00:00 2001
From: Simon Kelley <simon@thekelleys.org.uk>
Date: Mon, 25 Sep 2017 20:16:50 +0100
Subject: [PATCH 05/10] Security fix, CVE-2017-14495, OOM in DNS response
 creation.

Fix out-of-memory Dos vulnerability. An attacker which can
send malicious DNS queries to dnsmasq can trigger memory
allocations in the add_pseudoheader function
The allocated memory is never freed which leads to a DoS
through memory exhaustion. dnsmasq is vulnerable only
if one of the following option is specified:
--add-mac, --add-cpe-id or --add-subnet.
---
 src/edns0.c |  8 +++++++-
 1 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/edns0.c b/src/edns0.c
index 95b74ee..89b2692 100644
--- a/src/edns0.c
+++ b/src/edns0.c
@@ -192,9 +192,15 @@ size_t add_pseudoheader(struct dns_header *header, size_t plen, unsigned char *l
 	  !(p = skip_section(p, 
 			     ntohs(header->ancount) + ntohs(header->nscount) + ntohs(header->arcount), 
 			     header, plen)))
+      {
+	free(buff);
 	return plen;
+      }
       if (p + 11 > limit)
-       return plen; /* Too big */
+      {
+        free(buff);
+        return plen; /* Too big */
+      }
       *p++ = 0; /* empty name */
       PUTSHORT(T_OPT, p);
       PUTSHORT(udp_sz, p); /* max packet length, 512 if not given in EDNS0 header */
-- 
2.13.5