netdev - Re: [PATCH net v2] net: bridge: clear skb private space on bridge dev xmit

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Message-Id: <20200803.155835.1186341109955245993.davem@davemloft.net>
Date:   Mon, 03 Aug 2020 15:58:35 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     nikolay@...ulusnetworks.com
Cc:     netdev@...r.kernel.org, roopa@...ulusnetworks.com,
        bridge@...ts.linux-foundation.org, dsahern@...il.com
Subject: Re: [PATCH net v2] net: bridge: clear skb private space on bridge
 dev xmit

From: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
Date: Sun,  2 Aug 2020 15:50:39 +0300

> We need to clear all of the bridge private skb variables as they can be
> stale due to the packet having skb->cb initialized earlier 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 and were getting dropped. Same thing can in theory happen with the
> port isolation bit as well. We clear only the struct part after the bridge
> pointer (currently 8 bytes) since the pointer is always set later.
> We can now remove the redundant zeroing of frag_max_size.
> Also add a BUILD_BUG_ON to make sure we catch any movement of the bridge
> dev pointer.
> 
> Fixes: 821f1b21cabb ("bridge: add new BR_NEIGH_SUPPRESS port flag to suppress arp and nd flood")
> Signed-off-by: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>

Nikolay, I applied v1 already as I'm not at all against the full clear.