Author: np
Date: Wed Jan 24 05:09:21 2018
New Revision: 328314
URL: https://svnweb.freebsd.org/changeset/base/328314
Log:
  Do not generate illegal mbuf chains during IP fragment reassembly.  Only
  the first mbuf of the reassembled datagram should have a pkthdr.
  
  This was discovered with cxgbe(4) + IPSEC + ping with payload more than
  interface MTU.  cxgbe can generate !M_WRITEABLE mbufs and this results
  in m_unshare being called on the reassembled datagram, and it complains:
  
  panic: m_unshare: m0 0xfffff80020f82600, m 0xfffff8005d054100 has M_PKTHDR
  
  PR:           224922
  Reviewed by:  ae@
  MFC after:    1 week
  Sponsored by: Chelsio Communications
  Differential Revision:        https://reviews.freebsd.org/D14009

Modified:
  head/sys/netinet/ip_reass.c
  head/sys/netinet6/frag6.c

Modified: head/sys/netinet/ip_reass.c
==============================================================================
--- head/sys/netinet/ip_reass.c Wed Jan 24 04:29:16 2018        (r328313)
+++ head/sys/netinet/ip_reass.c Wed Jan 24 05:09:21 2018        (r328314)
@@ -377,6 +377,7 @@ ip_reass(struct mbuf *m)
                q->m_nextpkt = NULL;
                m->m_pkthdr.csum_flags &= q->m_pkthdr.csum_flags;
                m->m_pkthdr.csum_data += q->m_pkthdr.csum_data;
+               m_demote_pkthdr(q);
                m_cat(m, q);
        }
        /*

Modified: head/sys/netinet6/frag6.c
==============================================================================
--- head/sys/netinet6/frag6.c   Wed Jan 24 04:29:16 2018        (r328313)
+++ head/sys/netinet6/frag6.c   Wed Jan 24 05:09:21 2018        (r328314)
@@ -541,6 +541,7 @@ insert:
                while (t->m_next)
                        t = t->m_next;
                m_adj(IP6_REASS_MBUF(af6), af6->ip6af_offset);
+               m_demote_pkthdr(IP6_REASS_MBUF(af6));
                m_cat(t, IP6_REASS_MBUF(af6));
                free(af6, M_FTABLE);
                af6 = af6dwn;
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