netdev - Re: [PATCH net 2/2] net: bridge: fix lockdep multicast

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Message-ID: <1e8cda49-4bc3-6f0b-29f3-97848aab18f0@nvidia.com>
Date:   Mon, 26 Apr 2021 16:15:42 +0300
From:   Nikolay Aleksandrov <nikolay@...dia.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     Taehee Yoo <ap420073@...il.com>, davem@...emloft.net,
        kuba@...nel.org, dsahern@...nel.org, yoshfuji@...ux-ipv6.org,
        netdev@...r.kernel.org, j.vosburgh@...il.com, vfalico@...il.com,
        andy@...yhouse.net, roopa@...dia.com, ast@...nel.org,
        andriin@...com, daniel@...earbox.net, weiwan@...gle.com,
        cong.wang@...edance.com, bjorn@...nel.org,
        bridge@...ts.linux-foundation.org
Subject: Re: [PATCH net 2/2] net: bridge: fix lockdep multicast_lock false
 positive splat

On 26/04/2021 15:48, Herbert Xu wrote:
> On Sun, Apr 25, 2021 at 07:45:27PM +0300, Nikolay Aleksandrov wrote:
>>
>> Ugh.. that's just very ugly. :) The setup you've described above is by all means invalid, but
>> possible unfortunately. The bridge already checks if it's being added as a port to another
>> bridge, but not through multiple levels of indirection. These locks are completely unrelated
>> as they're in very different contexts (different devices).
> 
> Surely we should forbid this? Otherwise what's to stop someone
> from creating a loop?
> 
> Cheers,
> 

Indeed that would be best, it's very easy to loop them.