netfilter: cttimeout: fix buffer overflow

Chen Gang reports:
the length of nla_data(cda[CTA_TIMEOUT_NAME]) is not limited in server side.

And indeed, its used to strcpy to a fixed-sized buffer.

Fortunately, nfnetlink users need CAP_NET_ADMIN.
Reported-by: Chen Gang <gang.chen@asianux.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nfnetlink_cttimeout.c

@@ -41,7 +41,8 @@ MODULE_DESCRIPTION("cttimeout: Extended Netfilter Connection Tracking timeout tu
 static LIST_HEAD(cttimeout_list);
 
 static const struct nla_policy cttimeout_nla_policy[CTA_TIMEOUT_MAX+1] = {
-	[CTA_TIMEOUT_NAME]	= { .type = NLA_NUL_STRING },
+	[CTA_TIMEOUT_NAME]	= { .type = NLA_NUL_STRING,
+				    .len  = CTNL_TIMEOUT_NAME_MAX - 1},
 	[CTA_TIMEOUT_L3PROTO]	= { .type = NLA_U16 },
 	[CTA_TIMEOUT_L4PROTO]	= { .type = NLA_U8 },
 	[CTA_TIMEOUT_DATA]	= { .type = NLA_NESTED },