netdev - Re: [PATCH net] tun, bpf: fix suspicious RCU usage in tun_{attach,detach}

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Message-Id: <20160331.155032.901890572470890195.davem@davemloft.net>
Date:	Thu, 31 Mar 2016 15:50:32 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	hannes@...essinduktion.org
Cc:	daniel@...earbox.net, eric.dumazet@...il.com,
	alexei.starovoitov@...il.com, mkubecek@...e.cz,
	sasha.levin@...cle.com, jslaby@...e.cz, mst@...hat.com,
	netdev@...r.kernel.org
Subject: Re: [PATCH net] tun, bpf: fix suspicious RCU usage in
 tun_{attach,detach}_filter

From: Hannes Frederic Sowa <hannes@...essinduktion.org>
Date: Thu, 31 Mar 2016 21:48:27 +0200

> Tightest solution would probably be to combine both patches.
> 
> bool called_by_tuntap;
> 
> old_fp = rcu_dereference_protected(sk->sk_filter, called_by_tuntap ?
> lockdep_rtnl_is_held() : lockdep_sock_is_held());

Ok, I see what you're saying.

I misunderstood how the RTNL lockdep checks work and thought we could
get false positives from other entities taking RTNL.

Can you cook up the combined patch?

Thanks.