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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Nikolay Aleksandrov <nikolay@cumulusnetworks.com>,
        "David S. Miller" <davem@davemloft.net>,
        Huang Guobin <huangguobin4@huawei.com>
Subject: [PATCH 4.19 2/3] net: bridge: clear bridges private skb space on xmit
Date:   Thu, 27 Jan 2022 19:09:02 +0100
Message-Id: <20220127180256.913580967@linuxfoundation.org>
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From: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>

commit fd65e5a95d08389444e8591a20538b3edece0e15 upstream.

We need to clear all of the bridge private skb variables as they can be
stale due to the packet being recirculated through the stack and then
transmitted through the bridge device. Similar memset is already done on
bridge's input. We've seen cases where proxyarp_replied was 1 on routed
multicast packets transmitted through the bridge to ports with neigh
suppress which were getting dropped. Same thing can in theory happen with
the port isolation bit as well.

Fixes: 821f1b21cabb ("bridge: add new BR_NEIGH_SUPPRESS port flag to suppress arp and nd flood")
Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Huang Guobin <huangguobin4@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/bridge/br_device.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/net/bridge/br_device.c
+++ b/net/bridge/br_device.c
@@ -42,6 +42,8 @@ netdev_tx_t br_dev_xmit(struct sk_buff *
 	struct ethhdr *eth;
 	u16 vid = 0;
 
+	memset(skb->cb, 0, sizeof(struct br_input_skb_cb));
+
 	rcu_read_lock();
 	nf_ops = rcu_dereference(nf_br_ops);
 	if (nf_ops && nf_ops->br_dev_xmit_hook(skb)) {