linux-kernel - [PATCH] netfilter: nf_conntrack: reserve two bytes for nf_ct

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Message-Id: <1395934354-13226-1-git-send-email-avagin@openvz.org>
Date:	Thu, 27 Mar 2014 19:32:34 +0400
From:	Andrey Vagin <avagin@...nvz.org>
To:	linux-kernel@...r.kernel.org
Cc:	netfilter-devel@...r.kernel.org, netfilter@...r.kernel.org,
	coreteam@...filter.org, netdev@...r.kernel.org, vvs@...allels.com,
	Andrey Vagin <avagin@...nvz.org>,
	Pablo Neira Ayuso <pablo@...filter.org>,
	Patrick McHardy <kaber@...sh.net>,
	Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
	"David S. Miller" <davem@...emloft.net>
Subject: [PATCH] netfilter: nf_conntrack: reserve two bytes for nf_ct_ext->len

"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.

Cc: Pablo Neira Ayuso <pablo@...filter.org>
Cc: Patrick McHardy <kaber@...sh.net>
Cc: Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>
Cc: "David S. Miller" <davem@...emloft.net>
Signed-off-by: Andrey Vagin <avagin@...nvz.org>
---
 include/net/netfilter/nf_conntrack_extend.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/net/netfilter/nf_conntrack_extend.h b/include/net/netfilter/nf_conntrack_extend.h
index 956b175..36fd6bf 100644
--- a/include/net/netfilter/nf_conntrack_extend.h
+++ b/include/net/netfilter/nf_conntrack_extend.h
@@ -48,7 +48,7 @@ enum nf_ct_ext_id {
 struct nf_ct_ext {
 	struct rcu_head rcu;
 	u8 offset[NF_CT_EXT_NUM];
-	u8 len;
+	u16 len;
 	char data[0];
 };
 
-- 
1.8.5.3

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