[ 087/108] net-sched: sch_cbq: avoid infinite loop

Ben Hutchings
2012-10-07T23:22:53Z

From: Eric Dumazet <edumazet@google.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@visp.net.lb>
Tested-by: Denys Fedoryschenko <denys@visp.net.lb>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.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) {