linux-kernel - [ 087/108] net-sched: sch

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Message-Id: <20121007225846.722454035@decadent.org.uk>
Date:	Mon, 08 Oct 2012 00:00:01 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Eric Dumazet <edumazet@...gle.com>,
	Denys Fedoryschenko <denys@...p.net.lb>,
	"David S. Miller" <davem@...emloft.net>
Subject: [ 087/108] net-sched: sch_cbq: avoid infinite loop

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@...gle.com>

[ Upstream commit bdfc87f7d1e253e0a61e2fc6a75ea9d76f7fc03a ]

Its possible to setup a bad cbq configuration leading to
an infinite loop in cbq_classify()

DEV_OUT=eth0
ICMP="match ip protocol 1 0xff"
U32="protocol ip u32"
DST="match ip dst"
tc qdisc add dev $DEV_OUT root handle 1: cbq avpkt 1000 \
	bandwidth 100mbit
tc class add dev $DEV_OUT parent 1: classid 1:1 cbq \
	rate 512kbit allot 1500 prio 5 bounded isolated
tc filter add dev $DEV_OUT parent 1: prio 3 $U32 \
	$ICMP $DST 192.168.3.234 flowid 1:

Reported-by: Denys Fedoryschenko <denys@...p.net.lb>
Tested-by: Denys Fedoryschenko <denys@...p.net.lb>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/sched/sch_cbq.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/sched/sch_cbq.c b/net/sched/sch_cbq.c
index 24d94c0..599f67a 100644
--- a/net/sched/sch_cbq.c
+++ b/net/sched/sch_cbq.c
@@ -250,10 +250,11 @@ cbq_classify(struct sk_buff *skb, struct Qdisc *sch, int *qerr)
 			else if ((cl = defmap[res.classid & TC_PRIO_MAX]) == NULL)
 				cl = defmap[TC_PRIO_BESTEFFORT];
 
-			if (cl == NULL || cl->level >= head->level)
+			if (cl == NULL)
 				goto fallback;
 		}
-
+		if (cl->level >= head->level)
+			goto fallback;
 #ifdef CONFIG_NET_CLS_ACT
 		switch (result) {
 		case TC_ACT_QUEUED:


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