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From: Mark Johnston <markj@FreeBSD.org>
Date: Wed, 2 Mar 2016 05:01:58 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r296302 - head/sys/net80211
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Author: markj
Date: Wed Mar  2 05:01:58 2016
New Revision: 296302
URL: https://svnweb.freebsd.org/changeset/base/296302

Log:
  Use m_catpkt(9) to avoid a possible use-after-free in ieee80211_defrag().
  
  m is not guaranteed to be valid after m_cat() returns. The effects of this
  are most noticeable when INVARIANTS is enabled, since m's header length
  field is given a value of 0xdeadc0de by the trash dtor.
  
  Reviewed by:	glebius
  MFC after:	1 week
  Differential Revision:	https://reviews.freebsd.org/D5497

Modified:
  head/sys/net80211/ieee80211_input.c

Modified: head/sys/net80211/ieee80211_input.c
==============================================================================
--- head/sys/net80211/ieee80211_input.c	Wed Mar  2 04:58:51 2016	(r296301)
+++ head/sys/net80211/ieee80211_input.c	Wed Mar  2 05:01:58 2016	(r296302)
@@ -249,9 +249,7 @@ ieee80211_defrag(struct ieee80211_node *
 		mfrag = m;
 	} else {				/* concatenate */
 		m_adj(m, hdrspace);		/* strip header */
-		m_cat(mfrag, m);
-		/* NB: m_cat doesn't update the packet header */
-		mfrag->m_pkthdr.len += m->m_pkthdr.len;
+		m_catpkt(mfrag, m);
 		/* track last seqnum and fragno */
 		lwh = mtod(mfrag, struct ieee80211_frame *);
 		*(uint16_t *) lwh->i_seq = *(uint16_t *) wh->i_seq;