linux-kernel - Re: [PATCH] Remove broken netfilter binary sysctls from bridging code

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Message-ID: <m1fy18k5ru.fsf@ebiederm.dsl.xmission.com>
Date:	Thu, 20 Sep 2007 22:21:25 -0600
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, Patrick McHardy <kaber@...sh.net>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH] Remove broken netfilter binary sysctls from bridging code

jfannin@...il.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@...il.com>

Acked-by: "Eric W. Biederman" <ebiederm@...ssion.com>

> ---
>
>    This *really* needs to be reviewed by someone who knows what this
>    is all about.  I've simply extended the removal of netfilter binary
>    sysctl numbers so I could load bridge.ko.  I don't particularly
>    care if I get attributed for this fix or any of that.
>
>    It Works For Me.

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.

Eric
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