Linux Ethernet Bridging - Jan 2022 - [Bridge] [PATCH 4.19 1/1] net: bridge: clear bridge's private skb space on xmit

From: Nikolay Aleksandrov <nikolay at cumulusnetworks.com>

[ Upstream commit fd65e5a95d08389444e8591a20538b3edece0e15 ]

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 at cumulusnetworks.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Huang Guobin <huangguobin4 at huawei.com>
---
 net/bridge/br_device.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c
index a350c05b7ff5..7c6b1024dd4b 100644
--- 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 *skb, struct net_device
*dev)
 	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)) {
-- 
2.25.1

On Wed, Jan 26, 2022 at 11:36:39AM +0800, Huang Guobin
wrote:
> From: Nikolay Aleksandrov <nikolay at cumulusnetworks.com>
> 
> [ Upstream commit fd65e5a95d08389444e8591a20538b3edece0e15 ]
> 
> 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 at cumulusnetworks.com>
> Signed-off-by: David S. Miller <davem at davemloft.net>
> Signed-off-by: Huang Guobin <huangguobin4 at huawei.com>
> ---
>  net/bridge/br_device.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c
> index a350c05b7ff5..7c6b1024dd4b 100644
> --- 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 *skb, struct
net_device *dev)
>  	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)) {
> -- 
> 2.25.1
> 
Now queued up, thanks.

greg k-h