Date: Thu, 8 Nov 2018 20:17:36 +0000 (UTC) From: Ed Maste <emaste@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r340260 - head/sys/netinet Message-ID: <201811082017.wA8KHaxZ038910@repo.freebsd.org>
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Author: emaste Date: Thu Nov 8 20:17:36 2018 New Revision: 340260 URL: https://svnweb.freebsd.org/changeset/base/340260 Log: Avoid buffer underwrite in icmp_error icmp_error allocates either an mbuf (with pkthdr) or a cluster depending on the size of data to be quoted in the ICMP reply, but the calculation failed to account for the additional padding that m_align may apply. Include the ip header in the size passed to m_align. On 64-bit archs this will have the net effect of moving everything 4 bytes later in the mbuf or cluster. This will result in slightly pessimal alignment for the ICMP data copy. Also add an assertion that we do not move m_data before the beginning of the mbuf or cluster. Reported by: A reddit user Reviewed by: bz, jtl MFC after: 3 days Security: CVE-2018-17156 Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D17909 Modified: head/sys/netinet/ip_icmp.c Modified: head/sys/netinet/ip_icmp.c ============================================================================== --- head/sys/netinet/ip_icmp.c Thu Nov 8 19:56:45 2018 (r340259) +++ head/sys/netinet/ip_icmp.c Thu Nov 8 20:17:36 2018 (r340260) @@ -320,7 +320,8 @@ 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 @@ -362,6 +363,8 @@ 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;
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