diff --git a/include/linux/lsm_audit.h b/include/linux/lsm_audit.h
index 28f23b341c1c..cd23355d2271 100644
--- a/include/linux/lsm_audit.h
+++ b/include/linux/lsm_audit.h
@@ -26,7 +26,7 @@
 
 struct lsm_network_audit {
 	int netif;
-	struct sock *sk;
+	const struct sock *sk;
 	u16 family;
 	__be16 dport;
 	__be16 sport;
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 32a940117e7a..acc0494cceba 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -301,7 +301,7 @@ LSM_HOOK(void, LSM_RET_VOID, sk_clone_security, const struct sock *sk,
 	 struct sock *newsk)
 LSM_HOOK(void, LSM_RET_VOID, sk_getsecid, struct sock *sk, u32 *secid)
 LSM_HOOK(void, LSM_RET_VOID, sock_graft, struct sock *sk, struct socket *parent)
-LSM_HOOK(int, 0, inet_conn_request, struct sock *sk, struct sk_buff *skb,
+LSM_HOOK(int, 0, inet_conn_request, const struct sock *sk, struct sk_buff *skb,
 	 struct request_sock *req)
 LSM_HOOK(void, LSM_RET_VOID, inet_csk_clone, struct sock *newsk,
 	 const struct request_sock *req)
diff --git a/include/linux/security.h b/include/linux/security.h
index bc2725491560..0df62735651b 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1358,7 +1358,7 @@ void security_sk_clone(const struct sock *sk, struct sock *newsk);
 void security_sk_classify_flow(struct sock *sk, struct flowi *fl);
 void security_req_classify_flow(const struct request_sock *req, struct flowi *fl);
 void security_sock_graft(struct sock*sk, struct socket *parent);
-int security_inet_conn_request(struct sock *sk,
+int security_inet_conn_request(const struct sock *sk,
 			struct sk_buff *skb, struct request_sock *req);
 void security_inet_csk_clone(struct sock *newsk,
 			const struct request_sock *req);
@@ -1519,7 +1519,7 @@ static inline void security_sock_graft(struct sock *sk, struct socket *parent)
 {
 }
 
-static inline int security_inet_conn_request(struct sock *sk,
+static inline int security_inet_conn_request(const struct sock *sk,
 			struct sk_buff *skb, struct request_sock *req)
 {
 	return 0;
diff --git a/include/net/tcp.h b/include/net/tcp.h
index d5d22c411918..4525d6256321 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -2007,15 +2007,14 @@ struct tcp_request_sock_ops {
 					  const struct sock *sk,
 					  const struct sk_buff *skb);
 #endif
-	void (*init_req)(struct request_sock *req,
-			 const struct sock *sk_listener,
-			 struct sk_buff *skb);
 #ifdef CONFIG_SYN_COOKIES
 	__u32 (*cookie_init_seq)(const struct sk_buff *skb,
 				 __u16 *mss);
 #endif
-	struct dst_entry *(*route_req)(const struct sock *sk, struct flowi *fl,
-				       const struct request_sock *req);
+	struct dst_entry *(*route_req)(const struct sock *sk,
+				       struct sk_buff *skb,
+				       struct flowi *fl,
+				       struct request_sock *req);
 	u32 (*init_seq)(const struct sk_buff *skb);
 	u32 (*init_ts_off)(const struct net *net, const struct sk_buff *skb);
 	int (*send_synack)(const struct sock *sk, struct dst_entry *dst,
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index fb3a7750f623..9e8a6c1aa019 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6799,18 +6799,13 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
 	/* Note: tcp_v6_init_req() might override ir_iif for link locals */
 	inet_rsk(req)->ir_iif = inet_request_bound_dev_if(sk, skb);
 
-	af_ops->init_req(req, sk, skb);
-
-	if (security_inet_conn_request(sk, skb, req))
+	dst = af_ops->route_req(sk, skb, &fl, req);
+	if (!dst)
 		goto drop_and_free;
 
 	if (tmp_opt.tstamp_ok)
 		tcp_rsk(req)->ts_off = af_ops->init_ts_off(net, skb);
 
-	dst = af_ops->route_req(sk, &fl, req);
-	if (!dst)
-		goto drop_and_free;
-
 	if (!want_cookie && !isn) {
 		/* Kill the following clause, if you dislike this way. */
 		if (!net->ipv4.sysctl_tcp_syncookies &&
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index e4b31e70bd30..af2338294598 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1444,9 +1444,15 @@ static void tcp_v4_init_req(struct request_sock *req,
 }
 
 static struct dst_entry *tcp_v4_route_req(const struct sock *sk,
+					  struct sk_buff *skb,
 					  struct flowi *fl,
-					  const struct request_sock *req)
+					  struct request_sock *req)
 {
+	tcp_v4_init_req(req, sk, skb);
+
+	if (security_inet_conn_request(sk, skb, req))
+		return NULL;
+
 	return inet_csk_route_req(sk, &fl->u.ip4, req);
 }
 
@@ -1466,7 +1472,6 @@ const struct tcp_request_sock_ops tcp_request_sock_ipv4_ops = {
 	.req_md5_lookup	=	tcp_v4_md5_lookup,
 	.calc_md5_hash	=	tcp_v4_md5_hash_skb,
 #endif
-	.init_req	=	tcp_v4_init_req,
 #ifdef CONFIG_SYN_COOKIES
 	.cookie_init_seq =	cookie_v4_init_sequence,
 #endif
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 992cbf3eb9e3..1a1510513739 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -828,9 +828,15 @@ static void tcp_v6_init_req(struct request_sock *req,
 }
 
 static struct dst_entry *tcp_v6_route_req(const struct sock *sk,
+					  struct sk_buff *skb,
 					  struct flowi *fl,
-					  const struct request_sock *req)
+					  struct request_sock *req)
 {
+	tcp_v6_init_req(req, sk, skb);
+
+	if (security_inet_conn_request(sk, skb, req))
+		return NULL;
+
 	return inet6_csk_route_req(sk, &fl->u.ip6, req, IPPROTO_TCP);
 }
 
@@ -851,7 +857,6 @@ const struct tcp_request_sock_ops tcp_request_sock_ipv6_ops = {
 	.req_md5_lookup	=	tcp_v6_md5_lookup,
 	.calc_md5_hash	=	tcp_v6_md5_hash_skb,
 #endif
-	.init_req	=	tcp_v6_init_req,
 #ifdef CONFIG_SYN_COOKIES
 	.cookie_init_seq =	cookie_v6_init_sequence,
 #endif
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 023c856424b7..5f5815a1665f 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -112,9 +112,14 @@ static int __subflow_init_req(struct request_sock *req, const struct sock *sk_li
 	return 0;
 }
 
-static void subflow_init_req(struct request_sock *req,
-			     const struct sock *sk_listener,
-			     struct sk_buff *skb)
+/* Init mptcp request socket.
+ *
+ * Returns an error code if a JOIN has failed and a TCP reset
+ * should be sent.
+ */
+static int subflow_init_req(struct request_sock *req,
+			    const struct sock *sk_listener,
+			    struct sk_buff *skb)
 {
 	struct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk_listener);
 	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
@@ -125,7 +130,7 @@ static void subflow_init_req(struct request_sock *req,
 
 	ret = __subflow_init_req(req, sk_listener);
 	if (ret)
-		return;
+		return 0;
 
 	mptcp_get_options(skb, &mp_opt);
 
@@ -133,7 +138,7 @@ static void subflow_init_req(struct request_sock *req,
 		SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MPCAPABLEPASSIVE);
 
 		if (mp_opt.mp_join)
-			return;
+			return 0;
 	} else if (mp_opt.mp_join) {
 		SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINSYNRX);
 	}
@@ -157,7 +162,7 @@ static void subflow_init_req(struct request_sock *req,
 			} else {
 				subflow_req->mp_capable = 1;
 			}
-			return;
+			return 0;
 		}
 
 		err = mptcp_token_new_request(req);
@@ -175,7 +180,11 @@ static void subflow_init_req(struct request_sock *req,
 		subflow_req->remote_nonce = mp_opt.nonce;
 		subflow_req->msk = subflow_token_join_request(req, skb);
 
-		if (unlikely(req->syncookie) && subflow_req->msk) {
+		/* Can't fall back to TCP in this case. */
+		if (!subflow_req->msk)
+			return -EPERM;
+
+		if (unlikely(req->syncookie)) {
 			if (mptcp_can_accept_new_subflow(subflow_req->msk))
 				subflow_init_req_cookie_join_save(subflow_req, skb);
 		}
@@ -183,6 +192,8 @@ static void subflow_init_req(struct request_sock *req,
 		pr_debug("token=%u, remote_nonce=%u msk=%p", subflow_req->token,
 			 subflow_req->remote_nonce, subflow_req->msk);
 	}
+
+	return 0;
 }
 
 int mptcp_subflow_init_cookie_req(struct request_sock *req,
@@ -228,27 +239,53 @@ int mptcp_subflow_init_cookie_req(struct request_sock *req,
 }
 EXPORT_SYMBOL_GPL(mptcp_subflow_init_cookie_req);
 
-static void subflow_v4_init_req(struct request_sock *req,
-				const struct sock *sk_listener,
-				struct sk_buff *skb)
+static struct dst_entry *subflow_v4_route_req(const struct sock *sk,
+					      struct sk_buff *skb,
+					      struct flowi *fl,
+					      struct request_sock *req)
 {
+	struct dst_entry *dst;
+	int err;
+
 	tcp_rsk(req)->is_mptcp = 1;
 
-	tcp_request_sock_ipv4_ops.init_req(req, sk_listener, skb);
+	dst = tcp_request_sock_ipv4_ops.route_req(sk, skb, fl, req);
+	if (!dst)
+		return NULL;
 
-	subflow_init_req(req, sk_listener, skb);
+	err = subflow_init_req(req, sk, skb);
+	if (err == 0)
+		return dst;
+
+	dst_release(dst);
+	if (!req->syncookie)
+		tcp_request_sock_ops.send_reset(sk, skb);
+	return NULL;
 }
 
 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
-static void subflow_v6_init_req(struct request_sock *req,
-				const struct sock *sk_listener,
-				struct sk_buff *skb)
+static struct dst_entry *subflow_v6_route_req(const struct sock *sk,
+					      struct sk_buff *skb,
+					      struct flowi *fl,
+					      struct request_sock *req)
 {
+	struct dst_entry *dst;
+	int err;
+
 	tcp_rsk(req)->is_mptcp = 1;
 
-	tcp_request_sock_ipv6_ops.init_req(req, sk_listener, skb);
+	dst = tcp_request_sock_ipv6_ops.route_req(sk, skb, fl, req);
+	if (!dst)
+		return NULL;
 
-	subflow_init_req(req, sk_listener, skb);
+	err = subflow_init_req(req, sk, skb);
+	if (err == 0)
+		return dst;
+
+	dst_release(dst);
+	if (!req->syncookie)
+		tcp6_request_sock_ops.send_reset(sk, skb);
+	return NULL;
 }
 #endif
 
@@ -1388,7 +1425,7 @@ void __init mptcp_subflow_init(void)
 		panic("MPTCP: failed to init subflow request sock ops\n");
 
 	subflow_request_sock_ipv4_ops = tcp_request_sock_ipv4_ops;
-	subflow_request_sock_ipv4_ops.init_req = subflow_v4_init_req;
+	subflow_request_sock_ipv4_ops.route_req = subflow_v4_route_req;
 
 	subflow_specific = ipv4_specific;
 	subflow_specific.conn_request = subflow_v4_conn_request;
@@ -1397,7 +1434,7 @@ void __init mptcp_subflow_init(void)
 
 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 	subflow_request_sock_ipv6_ops = tcp_request_sock_ipv6_ops;
-	subflow_request_sock_ipv6_ops.init_req = subflow_v6_init_req;
+	subflow_request_sock_ipv6_ops.route_req = subflow_v6_route_req;
 
 	subflow_v6_specific = ipv6_specific;
 	subflow_v6_specific.conn_request = subflow_v6_conn_request;
diff --git a/security/apparmor/include/net.h b/security/apparmor/include/net.h
index 2431c011800d..aadb4b29fb66 100644
--- a/security/apparmor/include/net.h
+++ b/security/apparmor/include/net.h
@@ -107,6 +107,6 @@ int aa_sock_file_perm(struct aa_label *label, const char *op, u32 request,
 		      struct socket *sock);
 
 int apparmor_secmark_check(struct aa_label *label, char *op, u32 request,
-			   u32 secid, struct sock *sk);
+			   u32 secid, const struct sock *sk);
 
 #endif /* __AA_NET_H */
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index ffeaee5ed968..1b0aba8eb723 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -1147,7 +1147,7 @@ static void apparmor_sock_graft(struct sock *sk, struct socket *parent)
 }
 
 #ifdef CONFIG_NETWORK_SECMARK
-static int apparmor_inet_conn_request(struct sock *sk, struct sk_buff *skb,
+static int apparmor_inet_conn_request(const struct sock *sk, struct sk_buff *skb,
 				      struct request_sock *req)
 {
 	struct aa_sk_ctx *ctx = SK_CTX(sk);
diff --git a/security/apparmor/net.c b/security/apparmor/net.c
index fa0e85568450..e0c1b50d6edd 100644
--- a/security/apparmor/net.c
+++ b/security/apparmor/net.c
@@ -211,7 +211,7 @@ static int apparmor_secmark_init(struct aa_secmark *secmark)
 }
 
 static int aa_secmark_perm(struct aa_profile *profile, u32 request, u32 secid,
-			   struct common_audit_data *sa, struct sock *sk)
+			   struct common_audit_data *sa)
 {
 	int i, ret;
 	struct aa_perms perms = { };
@@ -244,13 +244,13 @@ static int aa_secmark_perm(struct aa_profile *profile, u32 request, u32 secid,
 }
 
 int apparmor_secmark_check(struct aa_label *label, char *op, u32 request,
-			   u32 secid, struct sock *sk)
+			   u32 secid, const struct sock *sk)
 {
 	struct aa_profile *profile;
 	DEFINE_AUDIT_SK(sa, op, sk);
 
 	return fn_for_each_confined(label, profile,
 				    aa_secmark_perm(profile, request, secid,
-						    &sa, sk));
+						    &sa));
 }
 #endif
diff --git a/security/lsm_audit.c b/security/lsm_audit.c
index 53d0d183db8f..078f9cdcd7f5 100644
--- a/security/lsm_audit.c
+++ b/security/lsm_audit.c
@@ -183,7 +183,7 @@ int ipv6_skb_to_auditdata(struct sk_buff *skb,
 
 
 static inline void print_ipv6_addr(struct audit_buffer *ab,
-				   struct in6_addr *addr, __be16 port,
+				   const struct in6_addr *addr, __be16 port,
 				   char *name1, char *name2)
 {
 	if (!ipv6_addr_any(addr))
@@ -322,7 +322,7 @@ static void dump_common_audit_data(struct audit_buffer *ab,
 	}
 	case LSM_AUDIT_DATA_NET:
 		if (a->u.net->sk) {
-			struct sock *sk = a->u.net->sk;
+			const struct sock *sk = a->u.net->sk;
 			struct unix_sock *u;
 			struct unix_address *addr;
 			int len = 0;
diff --git a/security/security.c b/security/security.c
index a28045dc9e7f..6509f95d203f 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2225,7 +2225,7 @@ void security_sock_graft(struct sock *sk, struct socket *parent)
 }
 EXPORT_SYMBOL(security_sock_graft);
 
-int security_inet_conn_request(struct sock *sk,
+int security_inet_conn_request(const struct sock *sk,
 			struct sk_buff *skb, struct request_sock *req)
 {
 	return call_int_hook(inet_conn_request, 0, sk, skb, req);
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 6b1826fc3658..6fa593006802 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -5355,7 +5355,7 @@ static void selinux_sctp_sk_clone(struct sctp_endpoint *ep, struct sock *sk,
 	selinux_netlbl_sctp_sk_clone(sk, newsk);
 }
 
-static int selinux_inet_conn_request(struct sock *sk, struct sk_buff *skb,
+static int selinux_inet_conn_request(const struct sock *sk, struct sk_buff *skb,
 				     struct request_sock *req)
 {
 	struct sk_security_struct *sksec = sk->sk_security;
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 5c90b9fa4d40..3a62d6aa74a6 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -3864,7 +3864,7 @@ static inline struct smack_known *smack_from_skb(struct sk_buff *skb)
  *
  * Returns smack_known of the IP options or NULL if that won't work.
  */
-static struct smack_known *smack_from_netlbl(struct sock *sk, u16 family,
+static struct smack_known *smack_from_netlbl(const struct sock *sk, u16 family,
 					     struct sk_buff *skb)
 {
 	struct netlbl_lsm_secattr secattr;
@@ -4114,7 +4114,7 @@ static void smack_sock_graft(struct sock *sk, struct socket *parent)
  * Returns 0 if a task with the packet label could write to
  * the socket, otherwise an error code
  */
-static int smack_inet_conn_request(struct sock *sk, struct sk_buff *skb,
+static int smack_inet_conn_request(const struct sock *sk, struct sk_buff *skb,
 				   struct request_sock *req)
 {
 	u16 family = sk->sk_family;