[Bridge] Patch "net: bridge: Fix ethernet header pointer before check skb forwardable" has been added to the 4.9-stable tree

gregkh at linuxfoundation.org gregkh at linuxfoundation.org
Sat Jan 26 10:07:06 UTC 2019

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

    net: bridge: Fix ethernet header pointer before check skb forwardable

to the 4.9-stable tree which can be found at:

The filename of the patch is:
and it can be found in the queue-4.9 subdirectory.

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

>From foo at baz Sat Jan 26 10:53:10 CET 2019
From: Yunjian Wang <wangyunjian at huawei.com>
Date: Thu, 17 Jan 2019 09:46:41 +0800
Subject: net: bridge: Fix ethernet header pointer before check skb forwardable

From: Yunjian Wang <wangyunjian at huawei.com>

[ Upstream commit 28c1382fa28f2e2d9d0d6f25ae879b5af2ecbd03 ]

The skb header should be set to ethernet header before using
is_skb_forwardable. Because the ethernet header length has been
considered in is_skb_forwardable(including dev->hard_header_len

To reproduce the issue:
1, add 2 ports on linux bridge br using following commands:
$ brctl addbr br
$ brctl addif br eth0
$ brctl addif br eth1
2, the MTU of eth0 and eth1 is 1500
3, send a packet(Data 1480, UDP 8, IP 20, Ethernet 14, VLAN 4)
from eth0 to eth1

So the expect result is packet larger than 1500 cannot pass through
eth0 and eth1. But currently, the packet passes through success, it
means eth1's MTU limit doesn't take effect.

Fixes: f6367b4660dd ("bridge: use is_skb_forwardable in forward path")
Cc: bridge at lists.linux-foundation.org
Cc: Nkolay Aleksandrov <nikolay at cumulusnetworks.com>
Cc: Roopa Prabhu <roopa at cumulusnetworks.com>
Cc: Stephen Hemminger <stephen at networkplumber.org>
Signed-off-by: Yunjian Wang <wangyunjian at huawei.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
 net/bridge/br_forward.c |    9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

--- a/net/bridge/br_forward.c
+++ b/net/bridge/br_forward.c
@@ -35,10 +35,10 @@ static inline int should_deliver(const s
 int br_dev_queue_push_xmit(struct net *net, struct sock *sk, struct sk_buff *skb)
+	skb_push(skb, ETH_HLEN);
 	if (!is_skb_forwardable(skb->dev, skb))
 		goto drop;
-	skb_push(skb, ETH_HLEN);
 	if (skb->ip_summed == CHECKSUM_PARTIAL &&
@@ -96,12 +96,11 @@ static void __br_forward(const struct ne
 		net = dev_net(indev);
 	} else {
 		if (unlikely(netpoll_tx_running(to->br->dev))) {
-			if (!is_skb_forwardable(skb->dev, skb)) {
+			skb_push(skb, ETH_HLEN);
+			if (!is_skb_forwardable(skb->dev, skb))
-			} else {
-				skb_push(skb, ETH_HLEN);
+			else
 				br_netpoll_send_skb(to, skb);
-			}
 		br_hook = NF_BR_LOCAL_OUT;

Patches currently in stable-queue which might be from wangyunjian at huawei.com are


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