To: linux-kernel@vger.kernel.org
From: Stephen Hemminger <shemminger@linux-foundation.org>
Subject: Re: [PATCH] Remove broken netfilter binary sysctls from bridging
 code
Date: Mon, 24 Sep 2007 13:14:58 -0700
Organization: Linux Foundation
Message-ID: <20070924131458.0daa4562@freepuppy.rosehill>
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	<20070921020554.GE31759@nineveh.local>
	<m1fy18k5ru.fsf@ebiederm.dsl.xmission.com>
	<46F7EC0A.9030506@trash.net>
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On Mon, 24 Sep 2007 18:55:38 +0200
Patrick McHardy <kaber@trash.net> wrote:

> Eric W. Biederman wrote:
> > jfannin@gmail.com (Joseph Fannin) writes:
> > 
> > 
> >>The netfilter sysctls in the bridging code don't set strategy routines:
> >>
> >> sysctl table check failed: /net/bridge/bridge-nf-call-arptables .3.10.1 Missing
> >>strategy
> >> sysctl table check failed: /net/bridge/bridge-nf-call-iptables .3.10.2 Missing
> >>strategy
> >> sysctl table check failed: /net/bridge/bridge-nf-call-ip6tables .3.10.3 Missing
> >>strategy
> >> sysctl table check failed: /net/bridge/bridge-nf-filter-vlan-tagged .3.10.4
> >>Missing strategy
> >> sysctl table check failed: /net/bridge/bridge-nf-filter-pppoe-tagged .3.10.5
> >>Missing strategy
> >>
> >>    These binary sysctls can't work. The binary sysctl numbers of
> >>other netfilter sysctls with this problem are being removed.  These
> >>need to go as well.
> >>
> >>Signed-off-by: Joseph Fannin <jfannin@gmail.com>
> > 
> > 
> > Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
> 
> 
> Queued for 2.6.24, thanks.
> 
> > Hmm.  This is an interesting case.  The proc method is forcing
> > the integer to be either 0 or 1 in a racy fashion.  But none of the
> > users appear to depend upon that.
> > 
> > So this is the least broken set of binary sysctls I have seen caught
> > by my check.
> > 
> > A really good fix would be to remove the binary side and then to
> > modify brnf_sysctl_call_tables to allocate a temporary ctl_table and
> > integer on the stack and only set ctl->data after we have normalized
> > the written value.  But since in practice nothing cares about
> > the race a better fix probably isn't worth it.
> 
> 
> I seem to be missing something, the entire brnf_sysctl_call_tables
> thing looks purely cosmetic to me, wouldn't it be better to simply
> remove it?


I agree, removing seems like a better option.  But probably need to go
through a 3-6mo warning period, since sysctl's are technically an API.


-- 
Stephen Hemminger <shemminger@linux-foundation.org>

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