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

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Message-Id: <20160331.154840.206151100376077818.davem@davemloft.net>
Date:	Thu, 31 Mar 2016 15:48:40 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	alexei.starovoitov@...il.com
Cc:	hannes@...essinduktion.org, daniel@...earbox.net,
	eric.dumazet@...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: Alexei Starovoitov <alexei.starovoitov@...il.com>
Date: Thu, 31 Mar 2016 12:31:56 -0700

> On Thu, Mar 31, 2016 at 09:24:12PM +0200, Hannes Frederic Sowa wrote:
>> Hello,
>> 
>> On 31.03.2016 21:21, David Miller wrote:
>> >From: Daniel Borkmann <daniel@...earbox.net>
>> >Date: Thu, 31 Mar 2016 14:16:18 +0200
>> >
>> >Alexei, do you really mind if I apply Danile's patch?
> 
> I don't have strong opinion either way.
> Though Hannes's patch below looks simpler and easier to backport.
> Yeah, I do care about backports quite a bit more nowadays :)

You know, I care a lot about backports too :)

But Hannes's patch has the same fundamental issue, I think.

If we accept both synchornization styles, false positives are more
likely.

And in the long term, we can fix the false positive possibilities with
the RTNL checks.