Patchwork [3/7] netfilter: nf_ct_helper: implement variable length helper private data

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Submitter Pablo Neira
Date June 4, 2012, 12:21 p.m.
Message ID <1338812485-4232-4-git-send-email-pablo@netfilter.org>
Download mbox | patch
Permalink /patch/162783/
State Superseded
Headers show

Comments

Pablo Neira - June 4, 2012, 12:21 p.m.
From: Pablo Neira Ayuso <pablo@netfilter.org>

This patch uses the new variable length conntrack extensions.

Instead of using union nf_conntrack_help that contain all the
helper private data information, we allocate variable length
area to store the private helper data.

This patch includes the modification of all existing helpers.
It also includes a couple of include header to avoid compilation
warnings.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 include/linux/netfilter/nf_conntrack_sip.h  |    1 +
 include/net/netfilter/nf_conntrack.h        |   35 ++-------------------
 include/net/netfilter/nf_conntrack_helper.h |   15 ++++++++-
 net/ipv4/netfilter/nf_nat_amanda.c          |    4 +--
 net/ipv4/netfilter/nf_nat_h323.c            |    8 ++---
 net/ipv4/netfilter/nf_nat_pptp.c            |    6 ++--
 net/ipv4/netfilter/nf_nat_sip.c             |   14 ++++-----
 net/ipv4/netfilter/nf_nat_tftp.c            |    4 +--
 net/netfilter/nf_conntrack_core.c           |    3 +-
 net/netfilter/nf_conntrack_ftp.c            |    3 +-
 net/netfilter/nf_conntrack_h323_main.c      |   16 ++++++----
 net/netfilter/nf_conntrack_helper.c         |   11 ++++---
 net/netfilter/nf_conntrack_netlink.c        |    4 +--
 net/netfilter/nf_conntrack_pptp.c           |   17 ++++++-----
 net/netfilter/nf_conntrack_proto_gre.c      |   16 +++++-----
 net/netfilter/nf_conntrack_sane.c           |    4 +--
 net/netfilter/nf_conntrack_sip.c            |   29 +++++++++---------
 net/netfilter/xt_CT.c                       |   44 ++++++++++++++++-----------
 18 files changed, 119 insertions(+), 115 deletions(-)
Jan Engelhardt - June 4, 2012, 1:06 p.m.
On Monday 2012-06-04 14:21, pablo@netfilter.org wrote:

>+static inline void *nfct_help_data(const struct nf_conn *ct)
>+{
>+	struct nf_conn_help *help;
>+
>+	help = nf_ct_ext_find(ct, NF_CT_EXT_HELPER);
>+
>+	return (void *)&help->data;
>+}

I think you wanted

	return help->data;

here. Remember that help->data is of type char[0] which is
convertible to char* - which is what you want,
while adding an extra & would turn that into the undesired (char[0])*.



>@@ -89,12 +59,13 @@ struct nf_conn_help {
> 	/* Helper. if any */
> 	struct nf_conntrack_helper __rcu *helper;
> 
>-	union nf_conntrack_help help;
>-
> 	struct hlist_head expectations;
> 
> 	/* Current number of expected connections */
> 	u8 expecting[NF_CT_MAX_EXPECT_CLASSES];
>+
>+	/* private helper information. */
>+	char data[0];

There is a now-standardized notation:

	char data[];



>@@ -218,13 +221,13 @@ int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
> 	}
> 
> 	if (help == NULL) {
>-		help = nf_ct_helper_ext_add(ct, flags);
>+		help = nf_ct_helper_ext_add(ct, helper, flags);
> 		if (help == NULL) {
> 			ret = -ENOMEM;
> 			goto out;
> 		}
> 	} else {
>-		memset(&help->help, 0, sizeof(help->help));
>+		memset(&help->data, 0, sizeof(helper->data_len));
> 	}

memset(help->data, 0, sizeof(helper->data_len));

>index 6f4b00a..30f5e12 100644
>--- a/net/netfilter/nf_conntrack_netlink.c
>+++ b/net/netfilter/nf_conntrack_netlink.c
>@@ -1218,7 +1218,7 @@ ctnetlink_change_helper(struct nf_conn *ct, const struct nlattr * const cda[])
> 		if (help->helper)
> 			return -EBUSY;
> 		/* need to zero data of old helper */
>-		memset(&help->help, 0, sizeof(help->help));
>+		memset(&help->data, 0, help->helper->data_len);

Here too.. memset(help->data,...
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Joe Perches - June 4, 2012, 1:09 p.m.
On Mon, 2012-06-04 at 15:06 +0200, Jan Engelhardt wrote:
> On Monday 2012-06-04 14:21, pablo@netfilter.org wrote:

> >@@ -218,13 +221,13 @@ int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
> > 	}
> > 
> > 	if (help == NULL) {
> >-		help = nf_ct_helper_ext_add(ct, flags);
> >+		help = nf_ct_helper_ext_add(ct, helper, flags);
> > 		if (help == NULL) {
> > 			ret = -ENOMEM;
> > 			goto out;
> > 		}
> > 	} else {
> >-		memset(&help->help, 0, sizeof(help->help));
> >+		memset(&help->data, 0, sizeof(helper->data_len));
> > 	}
> 
> memset(help->data, 0, sizeof(helper->data_len));

	memset(help->data, 0, helper->data_len);


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Jan Engelhardt - June 4, 2012, 1:16 p.m.
On Monday 2012-06-04 15:09, Joe Perches wrote:

>On Mon, 2012-06-04 at 15:06 +0200, Jan Engelhardt wrote:
>> On Monday 2012-06-04 14:21, pablo@netfilter.org wrote:
>
>> >@@ -218,13 +221,13 @@ int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
>> > 	}
>> > 
>> > 	if (help == NULL) {
>> >-		help = nf_ct_helper_ext_add(ct, flags);
>> >+		help = nf_ct_helper_ext_add(ct, helper, flags);
>> > 		if (help == NULL) {
>> > 			ret = -ENOMEM;
>> > 			goto out;
>> > 		}
>> > 	} else {
>> >-		memset(&help->help, 0, sizeof(help->help));
>> >+		memset(&help->data, 0, sizeof(helper->data_len));
>> > 	}
>> 
>> memset(help->data, 0, sizeof(helper->data_len));
>
>	memset(help->data, 0, helper->data_len);

I knew this looked suspect. With so many "sizeof"s, this spot was 
starting to look like a "mine is bigger" competition.
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Patch

diff --git a/include/linux/netfilter/nf_conntrack_sip.h b/include/linux/netfilter/nf_conntrack_sip.h
index feda699..34e19f8 100644
--- a/include/linux/netfilter/nf_conntrack_sip.h
+++ b/include/linux/netfilter/nf_conntrack_sip.h
@@ -3,6 +3,7 @@ 
 #ifdef __KERNEL__
 
 #include <linux/types.h>
+#include <net/netfilter/nf_conntrack_expect.h>
 
 #define SIP_PORT	5060
 #define SIP_TIMEOUT	3600
diff --git a/include/net/netfilter/nf_conntrack.h b/include/net/netfilter/nf_conntrack.h
index cce7f6a..7449bacd 100644
--- a/include/net/netfilter/nf_conntrack.h
+++ b/include/net/netfilter/nf_conntrack.h
@@ -39,36 +39,6 @@  union nf_conntrack_expect_proto {
 	/* insert expect proto private data here */
 };
 
-/* Add protocol helper include file here */
-#include <linux/netfilter/nf_conntrack_ftp.h>
-#include <linux/netfilter/nf_conntrack_pptp.h>
-#include <linux/netfilter/nf_conntrack_h323.h>
-#include <linux/netfilter/nf_conntrack_sane.h>
-#include <linux/netfilter/nf_conntrack_sip.h>
-
-/* per conntrack: application helper private data */
-union nf_conntrack_help {
-	/* insert conntrack helper private data (master) here */
-#if defined(CONFIG_NF_CONNTRACK_FTP) || defined(CONFIG_NF_CONNTRACK_FTP_MODULE)
-	struct nf_ct_ftp_master ct_ftp_info;
-#endif
-#if defined(CONFIG_NF_CONNTRACK_PPTP) || \
-    defined(CONFIG_NF_CONNTRACK_PPTP_MODULE)
-	struct nf_ct_pptp_master ct_pptp_info;
-#endif
-#if defined(CONFIG_NF_CONNTRACK_H323) || \
-    defined(CONFIG_NF_CONNTRACK_H323_MODULE)
-	struct nf_ct_h323_master ct_h323_info;
-#endif
-#if defined(CONFIG_NF_CONNTRACK_SANE) || \
-    defined(CONFIG_NF_CONNTRACK_SANE_MODULE)
-	struct nf_ct_sane_master ct_sane_info;
-#endif
-#if defined(CONFIG_NF_CONNTRACK_SIP) || defined(CONFIG_NF_CONNTRACK_SIP_MODULE)
-	struct nf_ct_sip_master ct_sip_info;
-#endif
-};
-
 #include <linux/types.h>
 #include <linux/skbuff.h>
 #include <linux/timer.h>
@@ -89,12 +59,13 @@  struct nf_conn_help {
 	/* Helper. if any */
 	struct nf_conntrack_helper __rcu *helper;
 
-	union nf_conntrack_help help;
-
 	struct hlist_head expectations;
 
 	/* Current number of expected connections */
 	u8 expecting[NF_CT_MAX_EXPECT_CLASSES];
+
+	/* private helper information. */
+	char data[0];
 };
 
 #include <net/netfilter/ipv4/nf_conntrack_ipv4.h>
diff --git a/include/net/netfilter/nf_conntrack_helper.h b/include/net/netfilter/nf_conntrack_helper.h
index 5f5a4d9..5afdcf2 100644
--- a/include/net/netfilter/nf_conntrack_helper.h
+++ b/include/net/netfilter/nf_conntrack_helper.h
@@ -11,6 +11,7 @@ 
 #define _NF_CONNTRACK_HELPER_H
 #include <net/netfilter/nf_conntrack.h>
 #include <net/netfilter/nf_conntrack_extend.h>
+#include <net/netfilter/nf_conntrack_expect.h>
 
 struct module;
 
@@ -23,6 +24,9 @@  struct nf_conntrack_helper {
 	struct module *me;		/* pointer to self */
 	const struct nf_conntrack_expect_policy *expect_policy;
 
+	/* length of internal data, ie. sizeof(struct nf_ct_*_master) */
+	size_t data_len;
+
 	/* Tuple of things we will help (compared against server response) */
 	struct nf_conntrack_tuple tuple;
 
@@ -48,7 +52,7 @@  nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum);
 extern int nf_conntrack_helper_register(struct nf_conntrack_helper *);
 extern void nf_conntrack_helper_unregister(struct nf_conntrack_helper *);
 
-extern struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp);
+extern struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, struct nf_conntrack_helper *helper, gfp_t gfp);
 
 extern int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
 				     gfp_t flags);
@@ -60,6 +64,15 @@  static inline struct nf_conn_help *nfct_help(const struct nf_conn *ct)
 	return nf_ct_ext_find(ct, NF_CT_EXT_HELPER);
 }
 
+static inline void *nfct_help_data(const struct nf_conn *ct)
+{
+	struct nf_conn_help *help;
+
+	help = nf_ct_ext_find(ct, NF_CT_EXT_HELPER);
+
+	return (void *)&help->data;
+}
+
 extern int nf_conntrack_helper_init(struct net *net);
 extern void nf_conntrack_helper_fini(struct net *net);
 
diff --git a/net/ipv4/netfilter/nf_nat_amanda.c b/net/ipv4/netfilter/nf_nat_amanda.c
index 7b22382..8973d6a 100644
--- a/net/ipv4/netfilter/nf_nat_amanda.c
+++ b/net/ipv4/netfilter/nf_nat_amanda.c
@@ -13,11 +13,11 @@ 
 #include <linux/skbuff.h>
 #include <linux/udp.h>
 
-#include <net/netfilter/nf_nat_helper.h>
-#include <net/netfilter/nf_nat_rule.h>
 #include <net/netfilter/nf_conntrack_helper.h>
 #include <net/netfilter/nf_conntrack_expect.h>
 #include <linux/netfilter/nf_conntrack_amanda.h>
+#include <net/netfilter/nf_nat_helper.h>
+#include <net/netfilter/nf_nat_rule.h>
 
 MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>");
 MODULE_DESCRIPTION("Amanda NAT helper");
diff --git a/net/ipv4/netfilter/nf_nat_h323.c b/net/ipv4/netfilter/nf_nat_h323.c
index 8253670..a83865a 100644
--- a/net/ipv4/netfilter/nf_nat_h323.c
+++ b/net/ipv4/netfilter/nf_nat_h323.c
@@ -99,7 +99,7 @@  static int set_sig_addr(struct sk_buff *skb, struct nf_conn *ct,
 			unsigned char **data,
 			TransportAddress *taddr, int count)
 {
-	const struct nf_ct_h323_master *info = &nfct_help(ct)->help.ct_h323_info;
+	const struct nf_ct_h323_master *info = nfct_help_data(ct);
 	int dir = CTINFO2DIR(ctinfo);
 	int i;
 	__be16 port;
@@ -182,7 +182,7 @@  static int nat_rtp_rtcp(struct sk_buff *skb, struct nf_conn *ct,
 			struct nf_conntrack_expect *rtp_exp,
 			struct nf_conntrack_expect *rtcp_exp)
 {
-	struct nf_ct_h323_master *info = &nfct_help(ct)->help.ct_h323_info;
+	struct nf_ct_h323_master *info = nfct_help_data(ct);
 	int dir = CTINFO2DIR(ctinfo);
 	int i;
 	u_int16_t nated_port;
@@ -337,7 +337,7 @@  static int nat_h245(struct sk_buff *skb, struct nf_conn *ct,
 		    TransportAddress *taddr, __be16 port,
 		    struct nf_conntrack_expect *exp)
 {
-	struct nf_ct_h323_master *info = &nfct_help(ct)->help.ct_h323_info;
+	struct nf_ct_h323_master *info = nfct_help_data(ct);
 	int dir = CTINFO2DIR(ctinfo);
 	u_int16_t nated_port = ntohs(port);
 
@@ -427,7 +427,7 @@  static int nat_q931(struct sk_buff *skb, struct nf_conn *ct,
 		    unsigned char **data, TransportAddress *taddr, int idx,
 		    __be16 port, struct nf_conntrack_expect *exp)
 {
-	struct nf_ct_h323_master *info = &nfct_help(ct)->help.ct_h323_info;
+	struct nf_ct_h323_master *info = nfct_help_data(ct);
 	int dir = CTINFO2DIR(ctinfo);
 	u_int16_t nated_port = ntohs(port);
 	union nf_inet_addr addr;
diff --git a/net/ipv4/netfilter/nf_nat_pptp.c b/net/ipv4/netfilter/nf_nat_pptp.c
index c273d58..3881408 100644
--- a/net/ipv4/netfilter/nf_nat_pptp.c
+++ b/net/ipv4/netfilter/nf_nat_pptp.c
@@ -49,7 +49,7 @@  static void pptp_nat_expected(struct nf_conn *ct,
 	const struct nf_nat_pptp *nat_pptp_info;
 	struct nf_nat_ipv4_range range;
 
-	ct_pptp_info = &nfct_help(master)->help.ct_pptp_info;
+	ct_pptp_info = nfct_help_data(master);
 	nat_pptp_info = &nfct_nat(master)->help.nat_pptp_info;
 
 	/* And here goes the grand finale of corrosion... */
@@ -123,7 +123,7 @@  pptp_outbound_pkt(struct sk_buff *skb,
 	__be16 new_callid;
 	unsigned int cid_off;
 
-	ct_pptp_info  = &nfct_help(ct)->help.ct_pptp_info;
+	ct_pptp_info = nfct_help_data(ct);
 	nat_pptp_info = &nfct_nat(ct)->help.nat_pptp_info;
 
 	new_callid = ct_pptp_info->pns_call_id;
@@ -192,7 +192,7 @@  pptp_exp_gre(struct nf_conntrack_expect *expect_orig,
 	struct nf_ct_pptp_master *ct_pptp_info;
 	struct nf_nat_pptp *nat_pptp_info;
 
-	ct_pptp_info  = &nfct_help(ct)->help.ct_pptp_info;
+	ct_pptp_info = nfct_help_data(ct);
 	nat_pptp_info = &nfct_nat(ct)->help.nat_pptp_info;
 
 	/* save original PAC call ID in nat_info */
diff --git a/net/ipv4/netfilter/nf_nat_sip.c b/net/ipv4/netfilter/nf_nat_sip.c
index aafc4b6..f49222e 100644
--- a/net/ipv4/netfilter/nf_nat_sip.c
+++ b/net/ipv4/netfilter/nf_nat_sip.c
@@ -73,7 +73,7 @@  static int map_addr(struct sk_buff *skb, unsigned int dataoff,
 	enum ip_conntrack_info ctinfo;
 	struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 	enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
-	struct nf_conn_help *help = nfct_help(ct);
+	struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
 	char buffer[sizeof("nnn.nnn.nnn.nnn:nnnnn")];
 	unsigned int buflen;
 	__be32 newaddr;
@@ -86,7 +86,7 @@  static int map_addr(struct sk_buff *skb, unsigned int dataoff,
 	} else if (ct->tuplehash[dir].tuple.dst.u3.ip == addr->ip &&
 		   ct->tuplehash[dir].tuple.dst.u.udp.port == port) {
 		newaddr = ct->tuplehash[!dir].tuple.src.u3.ip;
-		newport = help->help.ct_sip_info.forced_dport ? :
+		newport = ct_sip_info->forced_dport ? :
 			  ct->tuplehash[!dir].tuple.src.u.udp.port;
 	} else
 		return 1;
@@ -123,7 +123,7 @@  static unsigned int ip_nat_sip(struct sk_buff *skb, unsigned int dataoff,
 	enum ip_conntrack_info ctinfo;
 	struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 	enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
-	struct nf_conn_help *help = nfct_help(ct);
+	struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
 	unsigned int coff, matchoff, matchlen;
 	enum sip_header_types hdr;
 	union nf_inet_addr addr;
@@ -233,14 +233,14 @@  next:
 		return NF_DROP;
 
 	/* Mangle destination port for Cisco phones, then fix up checksums */
-	if (dir == IP_CT_DIR_REPLY && help->help.ct_sip_info.forced_dport) {
+	if (dir == IP_CT_DIR_REPLY && ct_sip_info->forced_dport) {
 		struct udphdr *uh;
 
 		if (!skb_make_writable(skb, skb->len))
 			return NF_DROP;
 
 		uh = (struct udphdr *)(skb->data + ip_hdrlen(skb));
-		uh->dest = help->help.ct_sip_info.forced_dport;
+		uh->dest = ct_sip_info->forced_dport;
 
 		if (!nf_nat_mangle_udp_packet(skb, ct, ctinfo, 0, 0, NULL, 0))
 			return NF_DROP;
@@ -297,7 +297,7 @@  static unsigned int ip_nat_sip_expect(struct sk_buff *skb, unsigned int dataoff,
 	enum ip_conntrack_info ctinfo;
 	struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 	enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
-	struct nf_conn_help *help = nfct_help(ct);
+	struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
 	__be32 newip;
 	u_int16_t port;
 	__be16 srcport;
@@ -313,7 +313,7 @@  static unsigned int ip_nat_sip_expect(struct sk_buff *skb, unsigned int dataoff,
 	/* If the signalling port matches the connection's source port in the
 	 * original direction, try to use the destination port in the opposite
 	 * direction. */
-	srcport = help->help.ct_sip_info.forced_dport ? :
+	srcport = ct_sip_info->forced_dport ? :
 		  ct->tuplehash[dir].tuple.src.u.udp.port;
 	if (exp->tuple.dst.u.udp.port == srcport)
 		port = ntohs(ct->tuplehash[!dir].tuple.dst.u.udp.port);
diff --git a/net/ipv4/netfilter/nf_nat_tftp.c b/net/ipv4/netfilter/nf_nat_tftp.c
index a2901bf..4a1c270 100644
--- a/net/ipv4/netfilter/nf_nat_tftp.c
+++ b/net/ipv4/netfilter/nf_nat_tftp.c
@@ -8,11 +8,11 @@ 
 #include <linux/module.h>
 #include <linux/udp.h>
 
-#include <net/netfilter/nf_nat_helper.h>
-#include <net/netfilter/nf_nat_rule.h>
 #include <net/netfilter/nf_conntrack_helper.h>
 #include <net/netfilter/nf_conntrack_expect.h>
 #include <linux/netfilter/nf_conntrack_tftp.h>
+#include <net/netfilter/nf_nat_helper.h>
+#include <net/netfilter/nf_nat_rule.h>
 
 MODULE_AUTHOR("Magnus Boden <mb@ozaba.mine.nu>");
 MODULE_DESCRIPTION("TFTP NAT helper");
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 32c5909..afa6939 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -822,7 +822,8 @@  init_conntrack(struct net *net, struct nf_conn *tmpl,
 		__set_bit(IPS_EXPECTED_BIT, &ct->status);
 		ct->master = exp->master;
 		if (exp->helper) {
-			help = nf_ct_helper_ext_add(ct, GFP_ATOMIC);
+			help = nf_ct_helper_ext_add(ct, exp->helper,
+						    GFP_ATOMIC);
 			if (help)
 				rcu_assign_pointer(help->helper, exp->helper);
 		}
diff --git a/net/netfilter/nf_conntrack_ftp.c b/net/netfilter/nf_conntrack_ftp.c
index 44e47c9..4bb771d 100644
--- a/net/netfilter/nf_conntrack_ftp.c
+++ b/net/netfilter/nf_conntrack_ftp.c
@@ -358,7 +358,7 @@  static int help(struct sk_buff *skb,
 	u32 seq;
 	int dir = CTINFO2DIR(ctinfo);
 	unsigned int uninitialized_var(matchlen), uninitialized_var(matchoff);
-	struct nf_ct_ftp_master *ct_ftp_info = &nfct_help(ct)->help.ct_ftp_info;
+	struct nf_ct_ftp_master *ct_ftp_info = nfct_help_data(ct);
 	struct nf_conntrack_expect *exp;
 	union nf_inet_addr *daddr;
 	struct nf_conntrack_man cmd = {};
@@ -554,6 +554,7 @@  static int __init nf_conntrack_ftp_init(void)
 		ftp[i][0].tuple.src.l3num = PF_INET;
 		ftp[i][1].tuple.src.l3num = PF_INET6;
 		for (j = 0; j < 2; j++) {
+			ftp[i][j].data_len = sizeof(struct nf_ct_ftp_master);
 			ftp[i][j].tuple.src.u.tcp.port = htons(ports[i]);
 			ftp[i][j].tuple.dst.protonum = IPPROTO_TCP;
 			ftp[i][j].expect_policy = &ftp_exp_policy;
diff --git a/net/netfilter/nf_conntrack_h323_main.c b/net/netfilter/nf_conntrack_h323_main.c
index 471b054..988e9c3 100644
--- a/net/netfilter/nf_conntrack_h323_main.c
+++ b/net/netfilter/nf_conntrack_h323_main.c
@@ -114,7 +114,7 @@  static int get_tpkt_data(struct sk_buff *skb, unsigned int protoff,
 			 struct nf_conn *ct, enum ip_conntrack_info ctinfo,
 			 unsigned char **data, int *datalen, int *dataoff)
 {
-	struct nf_ct_h323_master *info = &nfct_help(ct)->help.ct_h323_info;
+	struct nf_ct_h323_master *info = nfct_help_data(ct);
 	int dir = CTINFO2DIR(ctinfo);
 	const struct tcphdr *th;
 	struct tcphdr _tcph;
@@ -619,6 +619,7 @@  static const struct nf_conntrack_expect_policy h245_exp_policy = {
 static struct nf_conntrack_helper nf_conntrack_helper_h245 __read_mostly = {
 	.name			= "H.245",
 	.me			= THIS_MODULE,
+	.data_len		= sizeof(struct nf_ct_h323_master),
 	.tuple.src.l3num	= AF_UNSPEC,
 	.tuple.dst.protonum	= IPPROTO_UDP,
 	.help			= h245_help,
@@ -1172,6 +1173,7 @@  static struct nf_conntrack_helper nf_conntrack_helper_q931[] __read_mostly = {
 	{
 		.name			= "Q.931",
 		.me			= THIS_MODULE,
+		.data_len		= sizeof(struct nf_ct_h323_master),
 		.tuple.src.l3num	= AF_INET,
 		.tuple.src.u.tcp.port	= cpu_to_be16(Q931_PORT),
 		.tuple.dst.protonum	= IPPROTO_TCP,
@@ -1247,7 +1249,7 @@  static int expect_q931(struct sk_buff *skb, struct nf_conn *ct,
 		       unsigned char **data,
 		       TransportAddress *taddr, int count)
 {
-	struct nf_ct_h323_master *info = &nfct_help(ct)->help.ct_h323_info;
+	struct nf_ct_h323_master *info = nfct_help_data(ct);
 	int dir = CTINFO2DIR(ctinfo);
 	int ret = 0;
 	int i;
@@ -1362,7 +1364,7 @@  static int process_rrq(struct sk_buff *skb, struct nf_conn *ct,
 		       enum ip_conntrack_info ctinfo,
 		       unsigned char **data, RegistrationRequest *rrq)
 {
-	struct nf_ct_h323_master *info = &nfct_help(ct)->help.ct_h323_info;
+	struct nf_ct_h323_master *info = nfct_help_data(ct);
 	int ret;
 	typeof(set_ras_addr_hook) set_ras_addr;
 
@@ -1397,7 +1399,7 @@  static int process_rcf(struct sk_buff *skb, struct nf_conn *ct,
 		       enum ip_conntrack_info ctinfo,
 		       unsigned char **data, RegistrationConfirm *rcf)
 {
-	struct nf_ct_h323_master *info = &nfct_help(ct)->help.ct_h323_info;
+	struct nf_ct_h323_master *info = nfct_help_data(ct);
 	int dir = CTINFO2DIR(ctinfo);
 	int ret;
 	struct nf_conntrack_expect *exp;
@@ -1446,7 +1448,7 @@  static int process_urq(struct sk_buff *skb, struct nf_conn *ct,
 		       enum ip_conntrack_info ctinfo,
 		       unsigned char **data, UnregistrationRequest *urq)
 {
-	struct nf_ct_h323_master *info = &nfct_help(ct)->help.ct_h323_info;
+	struct nf_ct_h323_master *info = nfct_help_data(ct);
 	int dir = CTINFO2DIR(ctinfo);
 	int ret;
 	typeof(set_sig_addr_hook) set_sig_addr;
@@ -1478,7 +1480,7 @@  static int process_arq(struct sk_buff *skb, struct nf_conn *ct,
 		       enum ip_conntrack_info ctinfo,
 		       unsigned char **data, AdmissionRequest *arq)
 {
-	const struct nf_ct_h323_master *info = &nfct_help(ct)->help.ct_h323_info;
+	const struct nf_ct_h323_master *info = nfct_help_data(ct);
 	int dir = CTINFO2DIR(ctinfo);
 	__be16 port;
 	union nf_inet_addr addr;
@@ -1746,6 +1748,7 @@  static struct nf_conntrack_helper nf_conntrack_helper_ras[] __read_mostly = {
 	{
 		.name			= "RAS",
 		.me			= THIS_MODULE,
+		.data_len		= sizeof(struct nf_ct_h323_master),
 		.tuple.src.l3num	= AF_INET,
 		.tuple.src.u.udp.port	= cpu_to_be16(RAS_PORT),
 		.tuple.dst.protonum	= IPPROTO_UDP,
@@ -1755,6 +1758,7 @@  static struct nf_conntrack_helper nf_conntrack_helper_ras[] __read_mostly = {
 	{
 		.name			= "RAS",
 		.me			= THIS_MODULE,
+		.data_len		= sizeof(struct nf_ct_h323_master),
 		.tuple.src.l3num	= AF_INET6,
 		.tuple.src.u.udp.port	= cpu_to_be16(RAS_PORT),
 		.tuple.dst.protonum	= IPPROTO_UDP,
diff --git a/net/netfilter/nf_conntrack_helper.c b/net/netfilter/nf_conntrack_helper.c
index 4fa2ff9..e0d3f4b 100644
--- a/net/netfilter/nf_conntrack_helper.c
+++ b/net/netfilter/nf_conntrack_helper.c
@@ -161,11 +161,14 @@  nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
 }
 EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
 
-struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
+struct nf_conn_help *
+nf_ct_helper_ext_add(struct nf_conn *ct,
+		     struct nf_conntrack_helper *helper, gfp_t gfp)
 {
 	struct nf_conn_help *help;
 
-	help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
+	help = nf_ct_ext_add_length(ct, NF_CT_EXT_HELPER,
+				    helper->data_len, gfp);
 	if (help)
 		INIT_HLIST_HEAD(&help->expectations);
 	else
@@ -218,13 +221,13 @@  int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
 	}
 
 	if (help == NULL) {
-		help = nf_ct_helper_ext_add(ct, flags);
+		help = nf_ct_helper_ext_add(ct, helper, flags);
 		if (help == NULL) {
 			ret = -ENOMEM;
 			goto out;
 		}
 	} else {
-		memset(&help->help, 0, sizeof(help->help));
+		memset(&help->data, 0, sizeof(helper->data_len));
 	}
 
 	rcu_assign_pointer(help->helper, helper);
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 6f4b00a..30f5e12 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -1218,7 +1218,7 @@  ctnetlink_change_helper(struct nf_conn *ct, const struct nlattr * const cda[])
 		if (help->helper)
 			return -EBUSY;
 		/* need to zero data of old helper */
-		memset(&help->help, 0, sizeof(help->help));
+		memset(&help->data, 0, help->helper->data_len);
 	} else {
 		/* we cannot set a helper for an existing conntrack */
 		return -EOPNOTSUPP;
@@ -1440,7 +1440,7 @@  ctnetlink_create_conntrack(struct net *net, u16 zone,
 		} else {
 			struct nf_conn_help *help;
 
-			help = nf_ct_helper_ext_add(ct, GFP_ATOMIC);
+			help = nf_ct_helper_ext_add(ct, helper, GFP_ATOMIC);
 			if (help == NULL) {
 				err = -ENOMEM;
 				goto err2;
diff --git a/net/netfilter/nf_conntrack_pptp.c b/net/netfilter/nf_conntrack_pptp.c
index 31d56b2..6fed9ec 100644
--- a/net/netfilter/nf_conntrack_pptp.c
+++ b/net/netfilter/nf_conntrack_pptp.c
@@ -174,7 +174,7 @@  static int destroy_sibling_or_exp(struct net *net, struct nf_conn *ct,
 static void pptp_destroy_siblings(struct nf_conn *ct)
 {
 	struct net *net = nf_ct_net(ct);
-	const struct nf_conn_help *help = nfct_help(ct);
+	const struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
 	struct nf_conntrack_tuple t;
 
 	nf_ct_gre_keymap_destroy(ct);
@@ -182,16 +182,16 @@  static void pptp_destroy_siblings(struct nf_conn *ct)
 	/* try original (pns->pac) tuple */
 	memcpy(&t, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, sizeof(t));
 	t.dst.protonum = IPPROTO_GRE;
-	t.src.u.gre.key = help->help.ct_pptp_info.pns_call_id;
-	t.dst.u.gre.key = help->help.ct_pptp_info.pac_call_id;
+	t.src.u.gre.key = ct_pptp_info->pns_call_id;
+	t.dst.u.gre.key = ct_pptp_info->pac_call_id;
 	if (!destroy_sibling_or_exp(net, ct, &t))
 		pr_debug("failed to timeout original pns->pac ct/exp\n");
 
 	/* try reply (pac->pns) tuple */
 	memcpy(&t, &ct->tuplehash[IP_CT_DIR_REPLY].tuple, sizeof(t));
 	t.dst.protonum = IPPROTO_GRE;
-	t.src.u.gre.key = help->help.ct_pptp_info.pac_call_id;
-	t.dst.u.gre.key = help->help.ct_pptp_info.pns_call_id;
+	t.src.u.gre.key = ct_pptp_info->pac_call_id;
+	t.dst.u.gre.key = ct_pptp_info->pns_call_id;
 	if (!destroy_sibling_or_exp(net, ct, &t))
 		pr_debug("failed to timeout reply pac->pns ct/exp\n");
 }
@@ -269,7 +269,7 @@  pptp_inbound_pkt(struct sk_buff *skb,
 		 struct nf_conn *ct,
 		 enum ip_conntrack_info ctinfo)
 {
-	struct nf_ct_pptp_master *info = &nfct_help(ct)->help.ct_pptp_info;
+	struct nf_ct_pptp_master *info = nfct_help_data(ct);
 	u_int16_t msg;
 	__be16 cid = 0, pcid = 0;
 	typeof(nf_nat_pptp_hook_inbound) nf_nat_pptp_inbound;
@@ -396,7 +396,7 @@  pptp_outbound_pkt(struct sk_buff *skb,
 		  struct nf_conn *ct,
 		  enum ip_conntrack_info ctinfo)
 {
-	struct nf_ct_pptp_master *info = &nfct_help(ct)->help.ct_pptp_info;
+	struct nf_ct_pptp_master *info = nfct_help_data(ct);
 	u_int16_t msg;
 	__be16 cid = 0, pcid = 0;
 	typeof(nf_nat_pptp_hook_outbound) nf_nat_pptp_outbound;
@@ -506,7 +506,7 @@  conntrack_pptp_help(struct sk_buff *skb, unsigned int protoff,
 
 {
 	int dir = CTINFO2DIR(ctinfo);
-	const struct nf_ct_pptp_master *info = &nfct_help(ct)->help.ct_pptp_info;
+	const struct nf_ct_pptp_master *info = nfct_help_data(ct);
 	const struct tcphdr *tcph;
 	struct tcphdr _tcph;
 	const struct pptp_pkt_hdr *pptph;
@@ -592,6 +592,7 @@  static const struct nf_conntrack_expect_policy pptp_exp_policy = {
 static struct nf_conntrack_helper pptp __read_mostly = {
 	.name			= "pptp",
 	.me			= THIS_MODULE,
+	.data_len		= sizeof(struct nf_ct_pptp_master),
 	.tuple.src.l3num	= AF_INET,
 	.tuple.src.u.tcp.port	= cpu_to_be16(PPTP_CONTROL_PORT),
 	.tuple.dst.protonum	= IPPROTO_TCP,
diff --git a/net/netfilter/nf_conntrack_proto_gre.c b/net/netfilter/nf_conntrack_proto_gre.c
index 4bf6b4e..c04a363 100644
--- a/net/netfilter/nf_conntrack_proto_gre.c
+++ b/net/netfilter/nf_conntrack_proto_gre.c
@@ -110,10 +110,10 @@  int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir,
 {
 	struct net *net = nf_ct_net(ct);
 	struct netns_proto_gre *net_gre = net_generic(net, proto_gre_net_id);
-	struct nf_conn_help *help = nfct_help(ct);
+	struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
 	struct nf_ct_gre_keymap **kmp, *km;
 
-	kmp = &help->help.ct_pptp_info.keymap[dir];
+	kmp = &ct_pptp_info->keymap[dir];
 	if (*kmp) {
 		/* check whether it's a retransmission */
 		read_lock_bh(&net_gre->keymap_lock);
@@ -151,19 +151,19 @@  void nf_ct_gre_keymap_destroy(struct nf_conn *ct)
 {
 	struct net *net = nf_ct_net(ct);
 	struct netns_proto_gre *net_gre = net_generic(net, proto_gre_net_id);
-	struct nf_conn_help *help = nfct_help(ct);
+	struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
 	enum ip_conntrack_dir dir;
 
 	pr_debug("entering for ct %p\n", ct);
 
 	write_lock_bh(&net_gre->keymap_lock);
 	for (dir = IP_CT_DIR_ORIGINAL; dir < IP_CT_DIR_MAX; dir++) {
-		if (help->help.ct_pptp_info.keymap[dir]) {
+		if (ct_pptp_info->keymap[dir]) {
 			pr_debug("removing %p from list\n",
-				 help->help.ct_pptp_info.keymap[dir]);
-			list_del(&help->help.ct_pptp_info.keymap[dir]->list);
-			kfree(help->help.ct_pptp_info.keymap[dir]);
-			help->help.ct_pptp_info.keymap[dir] = NULL;
+				 ct_pptp_info->keymap[dir]);
+			list_del(&ct_pptp_info->keymap[dir]->list);
+			kfree(ct_pptp_info->keymap[dir]);
+			ct_pptp_info->keymap[dir] = NULL;
 		}
 	}
 	write_unlock_bh(&net_gre->keymap_lock);
diff --git a/net/netfilter/nf_conntrack_sane.c b/net/netfilter/nf_conntrack_sane.c
index ec3fc18..295429f 100644
--- a/net/netfilter/nf_conntrack_sane.c
+++ b/net/netfilter/nf_conntrack_sane.c
@@ -69,13 +69,12 @@  static int help(struct sk_buff *skb,
 	void *sb_ptr;
 	int ret = NF_ACCEPT;
 	int dir = CTINFO2DIR(ctinfo);
-	struct nf_ct_sane_master *ct_sane_info;
+	struct nf_ct_sane_master *ct_sane_info = nfct_help_data(ct);
 	struct nf_conntrack_expect *exp;
 	struct nf_conntrack_tuple *tuple;
 	struct sane_request *req;
 	struct sane_reply_net_start *reply;
 
-	ct_sane_info = &nfct_help(ct)->help.ct_sane_info;
 	/* Until there's been traffic both ways, don't look in packets. */
 	if (ctinfo != IP_CT_ESTABLISHED &&
 	    ctinfo != IP_CT_ESTABLISHED_REPLY)
@@ -203,6 +202,7 @@  static int __init nf_conntrack_sane_init(void)
 		sane[i][0].tuple.src.l3num = PF_INET;
 		sane[i][1].tuple.src.l3num = PF_INET6;
 		for (j = 0; j < 2; j++) {
+			sane[i][j].data_len = sizeof(struct nf_ct_sane_master);
 			sane[i][j].tuple.src.u.tcp.port = htons(ports[i]);
 			sane[i][j].tuple.dst.protonum = IPPROTO_TCP;
 			sane[i][j].expect_policy = &sane_exp_policy;
diff --git a/net/netfilter/nf_conntrack_sip.c b/net/netfilter/nf_conntrack_sip.c
index c2daabe..a627863 100644
--- a/net/netfilter/nf_conntrack_sip.c
+++ b/net/netfilter/nf_conntrack_sip.c
@@ -1075,12 +1075,12 @@  static int process_invite_response(struct sk_buff *skb, unsigned int dataoff,
 {
 	enum ip_conntrack_info ctinfo;
 	struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
-	struct nf_conn_help *help = nfct_help(ct);
+	struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
 
 	if ((code >= 100 && code <= 199) ||
 	    (code >= 200 && code <= 299))
 		return process_sdp(skb, dataoff, dptr, datalen, cseq);
-	else if (help->help.ct_sip_info.invite_cseq == cseq)
+	else if (ct_sip_info->invite_cseq == cseq)
 		flush_expectations(ct, true);
 	return NF_ACCEPT;
 }
@@ -1091,12 +1091,12 @@  static int process_update_response(struct sk_buff *skb, unsigned int dataoff,
 {
 	enum ip_conntrack_info ctinfo;
 	struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
-	struct nf_conn_help *help = nfct_help(ct);
+	struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
 
 	if ((code >= 100 && code <= 199) ||
 	    (code >= 200 && code <= 299))
 		return process_sdp(skb, dataoff, dptr, datalen, cseq);
-	else if (help->help.ct_sip_info.invite_cseq == cseq)
+	else if (ct_sip_info->invite_cseq == cseq)
 		flush_expectations(ct, true);
 	return NF_ACCEPT;
 }
@@ -1107,12 +1107,12 @@  static int process_prack_response(struct sk_buff *skb, unsigned int dataoff,
 {
 	enum ip_conntrack_info ctinfo;
 	struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
-	struct nf_conn_help *help = nfct_help(ct);
+	struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
 
 	if ((code >= 100 && code <= 199) ||
 	    (code >= 200 && code <= 299))
 		return process_sdp(skb, dataoff, dptr, datalen, cseq);
-	else if (help->help.ct_sip_info.invite_cseq == cseq)
+	else if (ct_sip_info->invite_cseq == cseq)
 		flush_expectations(ct, true);
 	return NF_ACCEPT;
 }
@@ -1123,13 +1123,13 @@  static int process_invite_request(struct sk_buff *skb, unsigned int dataoff,
 {
 	enum ip_conntrack_info ctinfo;
 	struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
-	struct nf_conn_help *help = nfct_help(ct);
+	struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
 	unsigned int ret;
 
 	flush_expectations(ct, true);
 	ret = process_sdp(skb, dataoff, dptr, datalen, cseq);
 	if (ret == NF_ACCEPT)
-		help->help.ct_sip_info.invite_cseq = cseq;
+		ct_sip_info->invite_cseq = cseq;
 	return ret;
 }
 
@@ -1154,7 +1154,7 @@  static int process_register_request(struct sk_buff *skb, unsigned int dataoff,
 {
 	enum ip_conntrack_info ctinfo;
 	struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
-	struct nf_conn_help *help = nfct_help(ct);
+	struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
 	enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 	unsigned int matchoff, matchlen;
 	struct nf_conntrack_expect *exp;
@@ -1235,7 +1235,7 @@  static int process_register_request(struct sk_buff *skb, unsigned int dataoff,
 
 store_cseq:
 	if (ret == NF_ACCEPT)
-		help->help.ct_sip_info.register_cseq = cseq;
+		ct_sip_info->register_cseq = cseq;
 	return ret;
 }
 
@@ -1245,7 +1245,7 @@  static int process_register_response(struct sk_buff *skb, unsigned int dataoff,
 {
 	enum ip_conntrack_info ctinfo;
 	struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
-	struct nf_conn_help *help = nfct_help(ct);
+	struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
 	enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 	union nf_inet_addr addr;
 	__be16 port;
@@ -1262,7 +1262,7 @@  static int process_register_response(struct sk_buff *skb, unsigned int dataoff,
 	 * responses, so we store the sequence number of the last valid
 	 * request and compare it here.
 	 */
-	if (help->help.ct_sip_info.register_cseq != cseq)
+	if (ct_sip_info->register_cseq != cseq)
 		return NF_ACCEPT;
 
 	if (code >= 100 && code <= 199)
@@ -1363,7 +1363,7 @@  static int process_sip_request(struct sk_buff *skb, unsigned int dataoff,
 {
 	enum ip_conntrack_info ctinfo;
 	struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
-	struct nf_conn_help *help = nfct_help(ct);
+	struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
 	enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 	unsigned int matchoff, matchlen;
 	unsigned int cseq, i;
@@ -1381,7 +1381,7 @@  static int process_sip_request(struct sk_buff *skb, unsigned int dataoff,
 				    &matchlen, &addr, &port) > 0 &&
 	    port != ct->tuplehash[dir].tuple.src.u.udp.port &&
 	    nf_inet_addr_cmp(&addr, &ct->tuplehash[dir].tuple.src.u3))
-		help->help.ct_sip_info.forced_dport = port;
+		ct_sip_info->forced_dport = port;
 
 	for (i = 0; i < ARRAY_SIZE(sip_handlers); i++) {
 		const struct sip_handler *handler;
@@ -1595,6 +1595,7 @@  static int __init nf_conntrack_sip_init(void)
 		sip[i][3].help = sip_help_tcp;
 
 		for (j = 0; j < ARRAY_SIZE(sip[i]); j++) {
+			sip[i][j].data_len = sizeof(struct nf_ct_sip_master);
 			sip[i][j].tuple.src.u.udp.port = htons(ports[i]);
 			sip[i][j].expect_policy = sip_exp_policy;
 			sip[i][j].expect_class_max = SIP_EXPECT_MAX;
diff --git a/net/netfilter/xt_CT.c b/net/netfilter/xt_CT.c
index 3746d8b..3641e1b 100644
--- a/net/netfilter/xt_CT.c
+++ b/net/netfilter/xt_CT.c
@@ -113,6 +113,8 @@  static int xt_ct_tg_check_v0(const struct xt_tgchk_param *par)
 		goto err3;
 
 	if (info->helper[0]) {
+		struct nf_conntrack_helper *helper;
+
 		ret = -ENOENT;
 		proto = xt_ct_find_proto(par);
 		if (!proto) {
@@ -121,19 +123,21 @@  static int xt_ct_tg_check_v0(const struct xt_tgchk_param *par)
 			goto err3;
 		}
 
-		ret = -ENOMEM;
-		help = nf_ct_helper_ext_add(ct, GFP_KERNEL);
-		if (help == NULL)
-			goto err3;
-
 		ret = -ENOENT;
-		help->helper = nf_conntrack_helper_try_module_get(info->helper,
-								  par->family,
-								  proto);
-		if (help->helper == NULL) {
+		helper = nf_conntrack_helper_try_module_get(info->helper,
+							    par->family,
+							    proto);
+		if (helper == NULL) {
 			pr_info("No such helper \"%s\"\n", info->helper);
 			goto err3;
 		}
+
+		ret = -ENOMEM;
+		help = nf_ct_helper_ext_add(ct, helper, GFP_KERNEL);
+		if (help == NULL)
+			goto err3;
+
+		help->helper = helper;
 	}
 
 	__set_bit(IPS_TEMPLATE_BIT, &ct->status);
@@ -203,6 +207,8 @@  static int xt_ct_tg_check_v1(const struct xt_tgchk_param *par)
 		goto err3;
 
 	if (info->helper[0]) {
+		struct nf_conntrack_helper *helper;
+
 		ret = -ENOENT;
 		proto = xt_ct_find_proto(par);
 		if (!proto) {
@@ -211,19 +217,21 @@  static int xt_ct_tg_check_v1(const struct xt_tgchk_param *par)
 			goto err3;
 		}
 
-		ret = -ENOMEM;
-		help = nf_ct_helper_ext_add(ct, GFP_KERNEL);
-		if (help == NULL)
-			goto err3;
-
 		ret = -ENOENT;
-		help->helper = nf_conntrack_helper_try_module_get(info->helper,
-								  par->family,
-								  proto);
-		if (help->helper == NULL) {
+		helper = nf_conntrack_helper_try_module_get(info->helper,
+							    par->family,
+							    proto);
+		if (helper == NULL) {
 			pr_info("No such helper \"%s\"\n", info->helper);
 			goto err3;
 		}
+
+		ret = -ENOMEM;
+		help = nf_ct_helper_ext_add(ct, helper, GFP_KERNEL);
+		if (help == NULL)
+			goto err3;
+
+		help->helper = helper;
 	}
 
 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT