From: Hannes Frederic Sowa <hannes@stressinduktion•org>
To: Alexei Starovoitov <alexei.starovoitov@gmail•com>,
Michal Kubecek <mkubecek@suse•cz>
Cc: Daniel Borkmann <daniel@iogearbox•net>,
davem@davemloft•net, sasha.levin@oracle•com, jslaby@suse•cz,
eric.dumazet@gmail•com, mst@redhat•com, netdev@vger•kernel.org
Subject: Re: [PATCH net] tun, bpf: fix suspicious RCU usage in tun_{attach,detach}_filter
Date: Thu, 31 Mar 2016 14:12:18 +0200 [thread overview]
Message-ID: <56FD1422.9030903@stressinduktion.org> (raw)
In-Reply-To: <20160331054301.GA57227@ast-mbp.thefacebook.com>
On 31.03.2016 07:43, Alexei Starovoitov wrote:
> On Thu, Mar 31, 2016 at 07:22:32AM +0200, Michal Kubecek wrote:
>> On Wed, Mar 30, 2016 at 10:08:10PM -0700, Alexei Starovoitov wrote:
>>> On Thu, Mar 31, 2016 at 07:01:15AM +0200, Michal Kubecek wrote:
>>>> On Wed, Mar 30, 2016 at 06:18:42PM -0700, Alexei Starovoitov wrote:
>>>>>
>>>>> kinda heavy patch to shut up lockdep.
>>>>> Can we do
>>>>> old_fp = rcu_dereference_protected(sk->sk_filter,
>>>>> sock_owned_by_user(sk) || lockdep_rtnl_is_held());
>>>>> and it always be correct?
>>>>> I think right now tun is the only such user, but if it's correct
>>>>> for tun, it's correct for future users too. If not correct then
>>>>> not correct for tun either.
>>>>> Or I'm missing something?
>>>>
>>>> Already discussed here:
>>>>
>>>> http://thread.gmane.org/gmane.linux.kernel/2158069/focus=405853
>>>
>>> I saw that. My point above was challenging 'less accurate' part.
>>>
>> Daniel's point was that lockdep_rtnl_is_held() does not mean "we hold
>> RTNL" but "someone holds RTNL" so that some other task holding RTNL at
>> the moment could make the check happy even when called by someone
>> supposed to own the socket.
>
> Of course... and that is the case for all rtnl_dereference() calls...
> yet we're not paranoid about it.
lockdep_rtnl_is_held actually checks *current if the currently running
code actually has the lock, no?
Bye,
Hannes
next prev parent reply other threads:[~2016-03-31 12:12 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-31 0:13 [PATCH net] tun, bpf: fix suspicious RCU usage in tun_{attach,detach}_filter Daniel Borkmann
2016-03-31 1:18 ` Alexei Starovoitov
2016-03-31 5:01 ` Michal Kubecek
2016-03-31 5:08 ` Alexei Starovoitov
2016-03-31 5:22 ` Michal Kubecek
2016-03-31 5:43 ` Alexei Starovoitov
2016-03-31 11:35 ` Daniel Borkmann
2016-03-31 11:59 ` Eric Dumazet
2016-03-31 12:16 ` Daniel Borkmann
2016-03-31 19:21 ` David Miller
2016-03-31 19:24 ` Hannes Frederic Sowa
2016-03-31 19:31 ` Alexei Starovoitov
2016-03-31 19:48 ` David Miller
2016-03-31 19:36 ` David Miller
2016-03-31 19:48 ` Hannes Frederic Sowa
2016-03-31 19:50 ` David Miller
2016-03-31 21:52 ` Daniel Borkmann
2016-03-31 23:31 ` Hannes Frederic Sowa
2016-03-31 12:12 ` Hannes Frederic Sowa [this message]
2016-03-31 9:15 ` Jiri Slaby
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