svn commit: r341089 - releng/11.2/sys/netinet

[Gordon Tetlow]

Author: gordon
Date: Tue Nov 27 19:43:16 2018
New Revision: 341089
URL: https://svnweb.freebsd.org/changeset/base/341089

Log:
  Fix ICMP buffer underwrite. [EN-18:13.icmp]
  
  Approved by:	so
  Security:	FreeBSD-EN-18:13.icmp
  Security:	CVE-2018-17156

Modified:
  releng/11.2/sys/netinet/ip_icmp.c

Modified: releng/11.2/sys/netinet/ip_icmp.c
==============================================================================
--- releng/11.2/sys/netinet/ip_icmp.c	Tue Nov 27 19:42:16 2018	(r341088)
+++ releng/11.2/sys/netinet/ip_icmp.c	Tue Nov 27 19:43:16 2018	(r341089)
@@ -310,7 +310,8 @@ stdreply:	icmpelen = max(8, min(V_icmp_quotelen, ntohs
 #endif
 	icmplen = min(icmplen, M_TRAILINGSPACE(m) -
 	    sizeof(struct ip) - ICMP_MINLEN);
-	m_align(m, ICMP_MINLEN + icmplen);
+	m_align(m, sizeof(struct ip) + ICMP_MINLEN + icmplen);
+	m->m_data += sizeof(struct ip);
 	m->m_len = ICMP_MINLEN + icmplen;
 
 	/* XXX MRT  make the outgoing packet use the same FIB
@@ -352,6 +353,8 @@ stdreply:	icmpelen = max(8, min(V_icmp_quotelen, ntohs
 	 * reply should bypass as well.
 	 */
 	m->m_flags |= n->m_flags & M_SKIP_FIREWALL;
+	KASSERT(M_LEADINGSPACE(m) >= sizeof(struct ip),
+	    ("insufficient space for ip header"));
 	m->m_data -= sizeof(struct ip);
 	m->m_len += sizeof(struct ip);
 	m->m_pkthdr.len = m->m_len;