[Bridge] [PATCH net] net: bridge: fix per-port af_packet sockets

David Miller davem at davemloft.net
Wed Apr 17 03:36:00 UTC 2019


From: Nikolay Aleksandrov <nikolay at cumulusnetworks.com>
Date: Thu, 11 Apr 2019 13:56:39 +0300

> When the commit below was introduced it changed two visible things:
>  - the skb was no longer passed through the protocol handlers with the
>    original device
>  - the skb was passed up the stack with skb->dev = bridge
> 
> The first change broke af_packet sockets on bridge ports. For example we
> use them for hostapd which listens for ETH_P_PAE packets on the ports.
> We discussed two possible fixes:
>  - create a clone and pass it through NF_HOOK(), act on the original skb
>    based on the result
>  - somehow signal to the caller from the okfn() that it was called,
>    meaning the skb is ok to be passed, which this patch is trying to
>    implement via returning 1 from the bridge link-local okfn()
> 
> Note that we rely on the fact that NF_QUEUE/STOLEN would return 0 and
> drop/error would return < 0 thus the okfn() is called only when the
> return was 1, so we signal to the caller that it was called by preserving
> the return value from nf_hook().
> 
> Fixes: 8626c56c8279 ("bridge: fix potential use-after-free when hook returns QUEUE or STOLEN verdict")
> Signed-off-by: Nikolay Aleksandrov <nikolay at cumulusnetworks.com>
> ---
> I plan to make a selftest for this one too. Once we agree on the fix.

This seems reasonable, applied and queued up for -stable, thanks Nikolay.


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