Patch "netem: fix a use after free" has been added to the 4.4-stable tree

Patch "netem: fix a use after free" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    netem: fix a use after free

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     netem-fix-a-use-after-free.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Wed Jul  6 16:50:47 PDT 2016
From: Eric Dumazet <edumazet@google.com>
Date: Mon, 20 Jun 2016 15:00:43 -0700
Subject: netem: fix a use after free

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 21de12ee5568fd1aec47890c72967abf791ac80a ]

If the packet was dropped by lower qdisc, then we must not
access it later.

Save qdisc_pkt_len(skb) in a temp variable.

Fixes: 2ccccf5fb43f ("net_sched: update hierarchical backlog too")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: WANG Cong <xiyou.wangcong@gmail.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/sched/sch_netem.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -650,14 +650,14 @@ deliver:
 #endif
 
 			if (q->qdisc) {
+				unsigned int pkt_len = qdisc_pkt_len(skb);
 				int err = qdisc_enqueue(skb, q->qdisc);
 
-				if (unlikely(err != NET_XMIT_SUCCESS)) {
-					if (net_xmit_drop_count(err)) {
-						qdisc_qstats_drop(sch);
-						qdisc_tree_reduce_backlog(sch, 1,
-									  qdisc_pkt_len(skb));
-					}
+				if (err != NET_XMIT_SUCCESS &&
+				    net_xmit_drop_count(err)) {
+					qdisc_qstats_drop(sch);
+					qdisc_tree_reduce_backlog(sch, 1,
+								  pkt_len);
 				}
 				goto tfifo_dequeue;
 			}


Patches currently in stable-queue which might be from edumazet@google.com are

queue-4.4/net-alx-work-around-the-dma-rx-overflow-issue.patch
queue-4.4/netem-fix-a-use-after-free.patch
queue-4.4/net_sched-fix-pfifo_head_drop-behavior-vs-backlog.patch