[CVE-2014-9715][Precise][Trusty] netfilter: nf_conntrack: reserve two bytes for nf_ct_ext->len

[Luis Henriques]

From: Andrey Vagin <avagin at openvz.org>

"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.

Fixes: 5b423f6a40a0 (netfilter: nf_conntrack: fix racy timer handling with reliable)
Cc: Pablo Neira Ayuso <pablo at netfilter.org>
Cc: Patrick McHardy <kaber at trash.net>
Cc: Jozsef Kadlecsik <kadlec at blackhole.kfki.hu>
Cc: "David S. Miller" <davem at davemloft.net>
Signed-off-by: Andrey Vagin <avagin at openvz.org>
Signed-off-by: Pablo Neira Ayuso <pablo at netfilter.org>
(cherry picked from commit 223b02d923ecd7c84cf9780bb3686f455d279279)
BugLink: https://bugs.launchpad.net/bugs/1442080
CVE-2014-9715
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 include/net/netfilter/nf_conntrack_extend.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/net/netfilter/nf_conntrack_extend.h b/include/net/netfilter/nf_conntrack_extend.h
index 956b175523ff..55d15049ab2f 100644
--- a/include/net/netfilter/nf_conntrack_extend.h
+++ b/include/net/netfilter/nf_conntrack_extend.h
@@ -47,8 +47,8 @@ enum nf_ct_ext_id {
 /* Extensions: optional stuff which isn't permanently in struct. */
 struct nf_ct_ext {
 	struct rcu_head rcu;
-	u8 offset[NF_CT_EXT_NUM];
-	u8 len;
+	u16 offset[NF_CT_EXT_NUM];
+	u16 len;
 	char data[0];
 };