netfilter: conntrack: check NULL when retrieving ct extension

nf_ct_ext_find() might return NULL if ct extension is not found.

Add also the null checks to:

- nfct_help()
- nfct_help_data()
- nfct_seqadj()
- nfct_nat()

This is defensive, for safety reasons.

nf_ct_ext_find() used to return NULL if the extension is stale for
unconfirmed conntracks if the genid validation fails.

Skip NULL check in nf_nat_inet_fn() given this is valid to be NULL
for non-initialized ct nat extensions.

While at it, fetch ct helper area in nf_ct_expect_related_report() only
once and pass it on to other ancilliary functions. Replace WARN_ON()
by WARN_ON_ONCE() in nf_ct_unlink_expect_report().

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netfilter/nf_conntrack_helper.h

@@ -136,6 +136,8 @@ 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);
+	if (!help)
+		return NULL;
 
 	return (void *)help->data;
 }

net/ipv4/netfilter/nf_nat_h323.c

@@ -100,6 +100,9 @@ static int set_sig_addr(struct sk_buff *skb, struct nf_conn *ct,
 	__be16 port;
 	union nf_inet_addr addr;
 
+	if (!info)
+		return -1;
+
 	for (i = 0; i < count; i++) {
 		if (get_h225_addr(ct, *data, &taddr[i], &addr, &port)) {
 			if (addr.ip == ct->tuplehash[dir].tuple.src.u3.ip &&
@@ -184,6 +187,9 @@ static int nat_rtp_rtcp(struct sk_buff *skb, struct nf_conn *ct,
 	int i;
 	u_int16_t nated_port;
 
+	if (!info)
+		return -1;
+
 	/* Set expectations for NAT */
 	rtp_exp->saved_proto.udp.port = rtp_exp->tuple.dst.u.udp.port;
 	rtp_exp->expectfn = nf_nat_follow_master;
@@ -325,6 +331,9 @@ static int nat_h245(struct sk_buff *skb, struct nf_conn *ct,
 	int dir = CTINFO2DIR(ctinfo);
 	u_int16_t nated_port = ntohs(port);
 
+	if (!info)
+		return -1;
+
 	/* Set expectations for NAT */
 	exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
 	exp->expectfn = nf_nat_follow_master;
@@ -404,6 +413,9 @@ static int nat_q931(struct sk_buff *skb, struct nf_conn *ct,
 	u_int16_t nated_port = ntohs(port);
 	union nf_inet_addr addr;
 
+	if (!info)
+		return -1;
+
 	/* Set expectations for NAT */
 	exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
 	exp->expectfn = ip_nat_q931_expect;

net/ipv4/netfilter/nf_nat_pptp.c

@@ -53,11 +53,13 @@ static void pptp_nat_expected(struct nf_conn *ct,
 	struct nf_conn_nat *nat;
 
 	nat = nf_ct_nat_ext_add(ct);
-	if (WARN_ON_ONCE(!nat))
+	if (!nat)
 		return;
 
 	nat_pptp_info = &nat->help.nat_pptp_info;
 	ct_pptp_info = nfct_help_data(master);
+	if (!ct_pptp_info)
+		return;
 
 	/* And here goes the grand finale of corrosion... */
 	if (exp->dir == IP_CT_DIR_ORIGINAL) {
@@ -132,11 +134,13 @@ pptp_outbound_pkt(struct sk_buff *skb,
 	__be16 new_callid;
 	unsigned int cid_off;
 
-	if (WARN_ON_ONCE(!nat))
+	if (!nat)
 		return NF_DROP;
 
 	nat_pptp_info = &nat->help.nat_pptp_info;
 	ct_pptp_info = nfct_help_data(ct);
+	if (!ct_pptp_info)
+		return NF_DROP;
 
 	new_callid = ct_pptp_info->pns_call_id;
 
@@ -204,11 +208,13 @@ pptp_exp_gre(struct nf_conntrack_expect *expect_orig,
 	struct nf_ct_pptp_master *ct_pptp_info;
 	struct nf_nat_pptp *nat_pptp_info;
 
-	if (WARN_ON_ONCE(!nat))
+	if (!nat)
 		return;
 
 	nat_pptp_info = &nat->help.nat_pptp_info;
 	ct_pptp_info = nfct_help_data(ct);
+	if (!ct_pptp_info)
+		return;
 
 	/* save original PAC call ID in nat_info */
 	nat_pptp_info->pac_call_id = ct_pptp_info->pac_call_id;
@@ -241,7 +247,7 @@ pptp_inbound_pkt(struct sk_buff *skb,
 	__be16 new_pcid;
 	unsigned int pcid_off;
 
-	if (WARN_ON_ONCE(!nat))
+	if (!nat)
 		return NF_DROP;
 
 	nat_pptp_info = &nat->help.nat_pptp_info;

net/netfilter/nf_conntrack_broadcast.c

@@ -29,6 +29,9 @@ int nf_conntrack_broadcast_help(struct sk_buff *skb,
 	struct nf_conn_help *help = nfct_help(ct);
 	__be32 mask = 0;
 
+	if (!help)
+		goto out;
+
 	/* we're only interested in locally generated packets */
 	if (skb->sk == NULL || !net_eq(nf_ct_net(ct), sock_net(skb->sk)))
 		goto out;

net/netfilter/nf_conntrack_expect.c

@@ -52,8 +52,7 @@ void nf_ct_unlink_expect_report(struct nf_conntrack_expect *exp,
 	struct nf_conntrack_net *cnet;
 
 	lockdep_nfct_expect_lock_held();
-	WARN_ON(!master_help);
-	WARN_ON(timer_pending(&exp->timeout));
+	WARN_ON_ONCE(timer_pending(&exp->timeout));
 
 	hlist_del_rcu(&exp->hnode);
 
@@ -61,7 +60,8 @@ void nf_ct_unlink_expect_report(struct nf_conntrack_expect *exp,
 	cnet->expect_count--;
 
 	hlist_del_rcu(&exp->lnode);
-	master_help->expecting[exp->class]--;
+	if (master_help)
+		master_help->expecting[exp->class]--;
 
 	nf_ct_expect_event_report(IPEXP_DESTROY, exp, portid, report);
 	nf_ct_expect_put(exp);
@@ -405,10 +405,10 @@ void nf_ct_expect_put(struct nf_conntrack_expect *exp)
 }
 EXPORT_SYMBOL_GPL(nf_ct_expect_put);
 
-static void nf_ct_expect_insert(struct nf_conntrack_expect *exp)
+static void nf_ct_expect_insert(struct nf_conntrack_expect *exp,
+				struct nf_conn_help *master_help)
 {
 	struct nf_conntrack_net *cnet;
-	struct nf_conn_help *master_help = nfct_help(exp->master);
 	struct nf_conntrack_helper *helper;
 	struct net *net = nf_ct_exp_net(exp);
 	unsigned int h = nf_ct_expect_dst_hash(net, &exp->tuple);
@@ -436,10 +436,9 @@ static void nf_ct_expect_insert(struct nf_conntrack_expect *exp)
 }
 
 /* Race with expectations being used means we could have none to find; OK. */
-static void evict_oldest_expect(struct nf_conn *master,
+static void evict_oldest_expect(struct nf_conn_help *master_help,
 				struct nf_conntrack_expect *new)
 {
-	struct nf_conn_help *master_help = nfct_help(master);
 	struct nf_conntrack_expect *exp, *last = NULL;
 
 	hlist_for_each_entry(exp, &master_help->expectations, lnode) {
@@ -452,13 +451,12 @@ static void evict_oldest_expect(struct nf_conn *master,
 }
 
 static inline int __nf_ct_expect_check(struct nf_conntrack_expect *expect,
+				       struct nf_conn_help *master_help,
 				       unsigned int flags)
 {
 	const struct nf_conntrack_expect_policy *p;
 	struct nf_conntrack_expect *i;
 	struct nf_conntrack_net *cnet;
-	struct nf_conn *master = expect->master;
-	struct nf_conn_help *master_help = nfct_help(master);
 	struct nf_conntrack_helper *helper;
 	struct net *net = nf_ct_exp_net(expect);
 	struct hlist_node *next;
@@ -467,10 +465,6 @@ static inline int __nf_ct_expect_check(struct nf_conntrack_expect *expect,
 
 	lockdep_nfct_expect_lock_held();
 
-	if (!master_help) {
-		ret = -ESHUTDOWN;
-		goto out;
-	}
 	h = nf_ct_expect_dst_hash(net, &expect->tuple);
 	hlist_for_each_entry_safe(i, next, &nf_ct_expect_hash[h], hnode) {
 		if (master_matches(i, expect, flags) &&
@@ -493,7 +487,7 @@ static inline int __nf_ct_expect_check(struct nf_conntrack_expect *expect,
 		p = &helper->expect_policy[expect->class];
 		if (p->max_expected &&
 		    master_help->expecting[expect->class] >= p->max_expected) {
-			evict_oldest_expect(master, expect);
+			evict_oldest_expect(master_help, expect);
 			if (master_help->expecting[expect->class]
 						>= p->max_expected) {
 				ret = -EMFILE;
@@ -514,14 +508,21 @@ static inline int __nf_ct_expect_check(struct nf_conntrack_expect *expect,
 int nf_ct_expect_related_report(struct nf_conntrack_expect *expect,
 				u32 portid, int report, unsigned int flags)
 {
+	struct nf_conn_help *master_help;
 	int ret;
 
 	spin_lock_bh(&nf_conntrack_expect_lock);
-	ret = __nf_ct_expect_check(expect, flags);
+	master_help = nfct_help(expect->master);
+	if (!master_help) {
+		ret = -ESHUTDOWN;
+		goto out;
+	}
+
+	ret = __nf_ct_expect_check(expect, master_help, flags);
 	if (ret < 0)
 		goto out;
 
-	nf_ct_expect_insert(expect);
+	nf_ct_expect_insert(expect, master_help);
 
 	nf_ct_expect_event_report(IPEXP_NEW, expect, portid, report);
 	spin_unlock_bh(&nf_conntrack_expect_lock);

net/netfilter/nf_conntrack_ftp.c

@@ -384,6 +384,9 @@ static int help(struct sk_buff *skb,
 	int found = 0, ends_in_nl;
 	nf_nat_ftp_hook_fn *nf_nat_ftp;
 
+	if (!ct_ftp_info)
+		return NF_DROP;
+
 	/* Until there's been traffic both ways, don't look in packets. */
 	if (ctinfo != IP_CT_ESTABLISHED &&
 	    ctinfo != IP_CT_ESTABLISHED_REPLY) {
@@ -545,6 +548,9 @@ static int nf_ct_ftp_from_nlattr(struct nlattr *attr, struct nf_conn *ct)
 {
 	struct nf_ct_ftp_master *ftp = nfct_help_data(ct);
 
+	if (!ftp)
+		return -ENOENT;
+
 	/* This conntrack has been injected from user-space, always pick up
 	 * sequence tracking. Otherwise, the first FTP command after the
 	 * failover breaks.

net/netfilter/nf_conntrack_h323_main.c

@@ -76,6 +76,9 @@ static int get_tpkt_data(struct sk_buff *skb, unsigned int protoff,
 	int tpktlen;
 	int tpktoff;
 
+	if (!info)
+		return 0;
+
 	/* Get TCP header */
 	th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
 	if (th == NULL)
@@ -1191,6 +1194,9 @@ static int expect_q931(struct sk_buff *skb, struct nf_conn *ct,
 	union nf_inet_addr addr;
 	struct nf_conntrack_expect *exp;
 
+	if (!info)
+		return -1;
+
 	/* Look for the first related address */
 	for (i = 0; i < count; i++) {
 		if (get_h225_addr(ct, *data, &taddr[i], &addr, &port) &&
@@ -1307,6 +1313,9 @@ static int process_rrq(struct sk_buff *skb, struct nf_conn *ct,
 	const struct nfct_h323_nat_hooks *nathook;
 	int ret;
 
+	if (!info)
+		return -1;
+
 	pr_debug("nf_ct_ras: RRQ\n");
 
 	ret = expect_q931(skb, ct, ctinfo, protoff, data,
@@ -1345,6 +1354,9 @@ static int process_rcf(struct sk_buff *skb, struct nf_conn *ct,
 	int ret;
 	struct nf_conntrack_expect *exp;
 
+	if (!info)
+		return -1;
+
 	pr_debug("nf_ct_ras: RCF\n");
 
 	nathook = rcu_dereference(nfct_h323_nat_hook);
@@ -1395,6 +1407,9 @@ static int process_urq(struct sk_buff *skb, struct nf_conn *ct,
 	int dir = CTINFO2DIR(ctinfo);
 	int ret;
 
+	if (!info)
+		return -1;
+
 	pr_debug("nf_ct_ras: URQ\n");
 
 	nathook = rcu_dereference(nfct_h323_nat_hook);
@@ -1429,6 +1444,9 @@ static int process_arq(struct sk_buff *skb, struct nf_conn *ct,
 	__be16 port;
 	union nf_inet_addr addr;
 
+	if (!info)
+		return 0;
+
 	pr_debug("nf_ct_ras: ARQ\n");
 
 	nathook = rcu_dereference(nfct_h323_nat_hook);

net/netfilter/nf_conntrack_pptp.c

@@ -198,6 +198,9 @@ pptp_inbound_pkt(struct sk_buff *skb, unsigned int protoff,
 	u_int16_t msg;
 	__be16 cid = 0, pcid = 0;
 
+	if (!info)
+		return NF_DROP;
+
 	msg = ntohs(ctlh->messageType);
 	pr_debug("inbound control message %s\n", pptp_msg_name(msg));
 
@@ -325,6 +328,9 @@ pptp_outbound_pkt(struct sk_buff *skb, unsigned int protoff,
 	u_int16_t msg;
 	__be16 cid = 0, pcid = 0;
 
+	if (!info)
+		return NF_DROP;
+
 	msg = ntohs(ctlh->messageType);
 	pr_debug("outbound control message %s\n", pptp_msg_name(msg));
 
@@ -443,6 +449,9 @@ conntrack_pptp_help(struct sk_buff *skb, unsigned int protoff,
 	int ret;
 	u_int16_t msg;
 
+	if (!info)
+		return NF_DROP;
+
 #if IS_ENABLED(CONFIG_NF_NAT)
 	if (!nf_ct_is_confirmed(ct) && (ct->status & IPS_NAT_MASK)) {
 		struct nf_conn_nat *nat = nf_ct_ext_find(ct, NF_CT_EXT_NAT);

net/netfilter/nf_conntrack_proto_gre.c

@@ -131,6 +131,9 @@ bool nf_ct_gre_keymap_add(struct nf_conn *ct,
 	struct nf_ct_gre_keymap *km_orig, *km_repl;
 	bool ret = false;
 
+	if (!ct_pptp_info)
+		return false;
+
 	km_orig = kmalloc_obj(*km_orig, GFP_ATOMIC);
 	if (!km_orig)
 		return false;
@@ -187,6 +190,9 @@ void nf_ct_gre_keymap_destroy(struct nf_conn *ct)
 	struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
 	enum ip_conntrack_dir dir;
 
+	if (!ct_pptp_info)
+		return;
+
 	pr_debug("entering for ct %p\n", ct);
 
 	spin_lock_bh(&keymap_lock);
@@ -389,6 +395,9 @@ void gre_pptp_destroy_siblings(struct nf_conn *ct)
 	const struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
 	struct nf_conntrack_tuple t;
 
+	if (!ct_pptp_info)
+		return;
+
 	nf_ct_gre_keymap_destroy(ct);
 
 	/* try original (pns->pac) tuple */

net/netfilter/nf_conntrack_sane.c

@@ -74,6 +74,9 @@ static int help(struct sk_buff *skb,
 		struct sane_reply_net_start repl;
 	} buf;
 
+	if (!ct_sane_info)
+		return NF_DROP;
+
 	/* Until there's been traffic both ways, don't look in packets. */
 	if (ctinfo != IP_CT_ESTABLISHED &&
 	    ctinfo != IP_CT_ESTABLISHED_REPLY)

net/netfilter/nf_conntrack_seqadj.c

@@ -18,9 +18,12 @@ int nf_ct_seqadj_init(struct nf_conn *ct, enum ip_conntrack_info ctinfo,
 		return 0;
 
 	spin_lock_bh(&ct->lock);
-	set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
-
 	seqadj = nfct_seqadj(ct);
+	if (!seqadj) {
+		spin_unlock_bh(&ct->lock);
+		return 0;
+	}
+	set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
 	this_way = &seqadj->seq[dir];
 	this_way->offset_before	 = off;
 	this_way->offset_after	 = off;
@@ -39,10 +42,8 @@ int nf_ct_seqadj_set(struct nf_conn *ct, enum ip_conntrack_info ctinfo,
 	if (off == 0)
 		return 0;
 
-	if (unlikely(!seqadj)) {
-		WARN_ONCE(1, "Missing nfct_seqadj_ext_add() setup call\n");
+	if (unlikely(!seqadj))
 		return 0;
-	}
 
 	set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
 
@@ -125,6 +126,9 @@ static unsigned int nf_ct_sack_adjust(struct sk_buff *skb,
 	struct nf_conn_seqadj *seqadj = nfct_seqadj(ct);
 	unsigned int dir, optoff, optend;
 
+	if (!seqadj)
+		return 0;
+
 	optoff = protoff + sizeof(struct tcphdr);
 	optend = protoff + tcph->doff * 4;
 
@@ -175,6 +179,9 @@ int nf_ct_seq_adjust(struct sk_buff *skb,
 	struct nf_ct_seqadj *this_way, *other_way;
 	int res = 1;
 
+	if (!seqadj)
+		return 0;
+
 	this_way  = &seqadj->seq[dir];
 	other_way = &seqadj->seq[!dir];
 

net/netfilter/nf_conntrack_sip.c

@@ -887,6 +887,9 @@ static int refresh_signalling_expectation(struct nf_conn *ct,
 	struct hlist_node *next;
 	int found = 0;
 
+	if (!help)
+		return 0;
+
 	spin_lock_bh(&nf_conntrack_expect_lock);
 	hlist_for_each_entry_safe(exp, next, &help->expectations, lnode) {
 		if (exp->class != SIP_EXPECT_SIGNALLING ||
@@ -910,6 +913,9 @@ static void flush_expectations(struct nf_conn *ct, bool media)
 	struct nf_conntrack_expect *exp;
 	struct hlist_node *next;
 
+	if (!help)
+		return;
+
 	spin_lock_bh(&nf_conntrack_expect_lock);
 	hlist_for_each_entry_safe(exp, next, &help->expectations, lnode) {
 		if ((exp->class != SIP_EXPECT_SIGNALLING) ^ media)
@@ -940,6 +946,11 @@ static int set_expected_rtp_rtcp(struct sk_buff *skb, unsigned int protoff,
 	u_int16_t base_port;
 	__be16 rtp_port, rtcp_port;
 	const struct nf_nat_sip_hooks *hooks;
+	struct nf_conn_help *help;
+
+	help = nfct_help(ct);
+	if (!help)
+		return NF_DROP;
 
 	saddr = NULL;
 	if (sip_direct_media) {
@@ -1002,7 +1013,7 @@ static int set_expected_rtp_rtcp(struct sk_buff *skb, unsigned int protoff,
 		exp = __nf_ct_expect_find(net, nf_ct_zone(ct), &tuple);
 
 		if (!exp || exp->master == ct ||
-		    exp->helper != nfct_help(ct)->helper ||
+		    exp->helper != help->helper ||
 		    exp->class != class)
 			break;
 #if IS_ENABLED(CONFIG_NF_NAT)
@@ -1227,6 +1238,9 @@ static int process_invite_response(struct sk_buff *skb, unsigned int protoff,
 	struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 	struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
 
+	if (!ct_sip_info)
+		return NF_DROP;
+
 	if ((code >= 100 && code <= 199) ||
 	    (code >= 200 && code <= 299))
 		return process_sdp(skb, protoff, dataoff, dptr, datalen, cseq);
@@ -1244,6 +1258,9 @@ static int process_update_response(struct sk_buff *skb, unsigned int protoff,
 	struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 	struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
 
+	if (!ct_sip_info)
+		return NF_DROP;
+
 	if ((code >= 100 && code <= 199) ||
 	    (code >= 200 && code <= 299))
 		return process_sdp(skb, protoff, dataoff, dptr, datalen, cseq);
@@ -1261,6 +1278,9 @@ static int process_prack_response(struct sk_buff *skb, unsigned int protoff,
 	struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
 	struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
 
+	if (!ct_sip_info)
+		return NF_DROP;
+
 	if ((code >= 100 && code <= 199) ||
 	    (code >= 200 && code <= 299))
 		return process_sdp(skb, protoff, dataoff, dptr, datalen, cseq);
@@ -1279,6 +1299,9 @@ static int process_invite_request(struct sk_buff *skb, unsigned int protoff,
 	struct nf_ct_sip_master *ct_sip_info = nfct_help_data(ct);
 	unsigned int ret;
 
+	if (!ct_sip_info)
+		return NF_DROP;
+
 	flush_expectations(ct, true);
 	ret = process_sdp(skb, protoff, dataoff, dptr, datalen, cseq);
 	if (ret == NF_ACCEPT)
@@ -1316,11 +1339,15 @@ static int process_register_request(struct sk_buff *skb, unsigned int protoff,
 	union nf_inet_addr *saddr, daddr;
 	const struct nf_nat_sip_hooks *hooks;
 	struct nf_conntrack_helper *helper;
+	struct nf_conn_help *help;
 	__be16 port;
 	u8 proto;
 	unsigned int expires = 0;
 	int ret;
 
+	if (!ct_sip_info)
+		return NF_DROP;
+
 	/* Expected connections can not register again. */
 	if (ct->status & IPS_EXPECTED)
 		return NF_ACCEPT;
@@ -1366,7 +1393,11 @@ static int process_register_request(struct sk_buff *skb, unsigned int protoff,
 		goto store_cseq;
 	}
 
-	helper = rcu_dereference(nfct_help(ct)->helper);
+	help = nfct_help(ct);
+	if (!help)
+		return NF_DROP;
+
+	helper = rcu_dereference(help->helper);
 	if (!helper)
 		return NF_DROP;
 
@@ -1421,6 +1452,9 @@ static int process_register_response(struct sk_buff *skb, unsigned int protoff,
 	unsigned int expires = 0;
 	int in_contact = 0, ret;
 
+	if (!ct_sip_info)
+		return NF_DROP;
+
 	/* According to RFC 3261, "UAs MUST NOT send a new registration until
 	 * they have received a final response from the registrar for the
 	 * previous one or the previous REGISTER request has timed out".
@@ -1550,6 +1584,9 @@ static int process_sip_request(struct sk_buff *skb, unsigned int protoff,
 	union nf_inet_addr addr;
 	__be16 port;
 
+	if (!ct_sip_info)
+		return NF_DROP;
+
 	/* Many Cisco IP phones use a high source port for SIP requests, but
 	 * listen for the response on port 5060.  If we are the local
 	 * router for one of these phones, save the port number from the

net/netfilter/nf_nat_sip.c

@@ -106,6 +106,9 @@ static int map_addr(struct sk_buff *skb, unsigned int protoff,
 	union nf_inet_addr newaddr;
 	__be16 newport;
 
+	if (!ct_sip_info)
+		return 0;
+
 	if (nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.src.u3, addr) &&
 	    ct->tuplehash[dir].tuple.src.u.udp.port == port) {
 		newaddr = ct->tuplehash[!dir].tuple.dst.u3;
@@ -158,6 +161,9 @@ static unsigned int nf_nat_sip(struct sk_buff *skb, unsigned int protoff,
 	__be16 port;
 	int request, in_header;
 
+	if (!ct_sip_info)
+		return NF_DROP;
+
 	/* Basic rules: requests and responses. */
 	if (strncasecmp(*dptr, "SIP/2.0", strlen("SIP/2.0")) != 0) {
 		if (ct_sip_parse_request(ct, *dptr, *datalen,
@@ -326,6 +332,9 @@ static void nf_nat_sip_expected(struct nf_conn *ct,
 	int range_set_for_snat = 0;
 	struct nf_nat_range2 range;
 
+	if (!help)
+		return;
+
 	/* This must be a fresh one. */
 	BUG_ON(ct->status & IPS_NAT_DONE_MASK);
 
@@ -390,6 +399,9 @@ static unsigned int nf_nat_sip_expect(struct sk_buff *skb, unsigned int protoff,
 	char buffer[INET6_ADDRSTRLEN + sizeof("[]:nnnnn")];
 	unsigned int buflen;
 
+	if (!ct_sip_info)
+		return NF_DROP;
+
 	/* Connection will come from reply */
 	if (nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.src.u3,
 			     &ct->tuplehash[!dir].tuple.dst.u3))

net/netfilter/nfnetlink_cthelper.c

@@ -101,6 +101,9 @@ nfnl_cthelper_from_nlattr(struct nlattr *attr, struct nf_conn *ct)
 	struct nf_conn_help *help = nfct_help(ct);
 	const struct nf_conntrack_helper *helper;
 
+	if (!help)
+		return -EINVAL;
+
 	if (attr == NULL)
 		return -EINVAL;
 
@@ -118,6 +121,9 @@ nfnl_cthelper_to_nlattr(struct sk_buff *skb, const struct nf_conn *ct)
 	const struct nf_conn_help *help = nfct_help(ct);
 	const struct nf_conntrack_helper *helper;
 
+	if (!help)
+		return 0;
+
 	helper = rcu_dereference(help->helper);
 	if (helper && helper->data_len &&
 	    nla_put(skb, CTA_HELP_INFO, helper->data_len, &help->data))