netdev - Re: [PATCH] netfilter: nf_conntrack: reserve two bytes for nf_ct

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Message-ID: <20140330113504.GA5895@localhost>
Date:	Sun, 30 Mar 2014 13:35:04 +0200
From:	Pablo Neira Ayuso <pablo@...filter.org>
To:	Andrey Vagin <avagin@...nvz.org>
Cc:	linux-kernel@...r.kernel.org, netfilter-devel@...r.kernel.org,
	netfilter@...r.kernel.org, coreteam@...filter.org,
	netdev@...r.kernel.org, vvs@...allels.com,
	Patrick McHardy <kaber@...sh.net>,
	Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH] netfilter: nf_conntrack: reserve two bytes for
 nf_ct_ext->len (v3)

On Fri, Mar 28, 2014 at 01:54:32PM +0400, Andrey Vagin wrote:
> "len" contains sizeof(nf_ct_ext) and size of extensions. In a worst
> case it can contain all extensions. Bellow you can find sizes for all
> types of extensions. Their sum is definitely bigger than 256.
> 
> nf_ct_ext_types[0]->len = 24
> nf_ct_ext_types[1]->len = 32
> nf_ct_ext_types[2]->len = 24
> nf_ct_ext_types[3]->len = 32
> nf_ct_ext_types[4]->len = 152
> nf_ct_ext_types[5]->len = 2
> nf_ct_ext_types[6]->len = 16
> nf_ct_ext_types[7]->len = 8
> 
> I have seen "len" up to 280 and my host has crashes w/o this patch.
> 
> The right way to fix this problem is reducing the size of the ecache
> extension (4) and Florian is going to do this, but these changes will
> be quite large to be appropriate for a stable tree.
> 
> v2: rearrange the extension so ECACHE comes last. This is required to
> prevent overflow of nf_ct_ext->offset.
> v3: The previous attempt of rearranging constants doesn't work here,
> because extensions may be added in a random order.

Applied, thanks.
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