svn commit: r244025 - head/sys/net80211

[Adrian Chadd]

Author: adrian
Date: Sat Dec  8 09:48:03 2012
New Revision: 244025
URL: http://svnweb.freebsd.org/changeset/base/244025

Log:
  Fix a use-after-free bug in the Atheros fast-frames support.
  
  Tested:
  
  * AR5212 AP, AR5413 STA, iperf TCP STA->AP, destroyed and/or shutdown
    the STA vap during active iperf TCP traffic.
  
  PR:		kern/174273
  MFC after:	1 week

Modified:
  head/sys/net80211/ieee80211_superg.c

Modified: head/sys/net80211/ieee80211_superg.c
==============================================================================
--- head/sys/net80211/ieee80211_superg.c	Sat Dec  8 09:23:05 2012	(r244024)
+++ head/sys/net80211/ieee80211_superg.c	Sat Dec  8 09:48:03 2012	(r244025)
@@ -784,7 +784,7 @@ ieee80211_ff_node_cleanup(struct ieee802
 	struct ieee80211com *ic = ni->ni_ic;
 	struct ieee80211_superg *sg = ic->ic_superg;
 	struct ieee80211_tx_ampdu *tap;
-	struct mbuf *m, *head;
+	struct mbuf *m, *next_m, *head;
 	int tid;
 
 	IEEE80211_LOCK(ic);
@@ -803,9 +803,16 @@ ieee80211_ff_node_cleanup(struct ieee802
 	}
 	IEEE80211_UNLOCK(ic);
 
-	for (m = head; m != NULL; m = m->m_nextpkt) {
+	/*
+	 * Free mbufs, taking care to not dereference the mbuf after
+	 * we free it (hence grabbing m_nextpkt before we free it.)
+	 */
+	m = head;
+	while (m != NULL) {
+		next_m = m->m_nextpkt;
 		m_freem(m);
 		ieee80211_free_node(ni);
+		m = next_m;
 	}
 }