diff --git a/net/mptcp/fastopen.c b/net/mptcp/fastopen.c
index 082c46c0f50e..f717750906ff 100644
--- a/net/mptcp/fastopen.c
+++ b/net/mptcp/fastopen.c
@@ -24,12 +24,13 @@ void mptcp_fastopen_subflow_synack_set_params(struct mptcp_subflow_context *subf
 	sk = subflow->conn;
 	tp = tcp_sk(ssk);
 
-	subflow->is_mptfo = 1;
-
+	/* A valid TFO cookie does not guarantee SYN data. */
 	skb = skb_peek(&ssk->sk_receive_queue);
-	if (WARN_ON_ONCE(!skb))
+	if (!skb)
 		return;
 
+	subflow->is_mptfo = 1;
+
 	/* dequeue the skb from sk receive queue */
 	__skb_unlink(skb, &ssk->sk_receive_queue);
 	skb_ext_reset(skb);
diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index c664023d37ba..1057d500577b 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -50,6 +50,14 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 			}
 		}
 
+		/* Only the MPC + ACK can be used with a RM_ADDR */
+		if (subopt == OPTION_MPTCP_MPC_ACK) {
+			if ((mp_opt->suboptions & ~OPTION_MPTCP_RM_ADDR) != 0)
+				break;
+		} else if (mp_opt->suboptions != 0) {
+			break;
+		}
+
 		/* Cfr RFC 8684 Section 3.3.0:
 		 * If a checksum is present but its use had
 		 * not been negotiated in the MP_CAPABLE handshake, the receiver MUST
@@ -122,6 +130,11 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 		break;
 
 	case MPTCPOPT_MP_JOIN:
+		/* Can be used with a restricted number of other options */
+		if ((mp_opt->suboptions & ~(OPTION_MPTCP_RM_ADDR |
+					    OPTION_MPTCP_PRIO)) != 0)
+			break;
+
 		if (opsize == TCPOLEN_MPTCP_MPJ_SYN) {
 			mp_opt->suboptions |= OPTION_MPTCP_MPJ_SYN;
 			mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
@@ -153,6 +166,14 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 		break;
 
 	case MPTCPOPT_DSS:
+		/* Can be used with a restricted number of other options */
+		if ((mp_opt->suboptions & ~(OPTION_MPTCP_ADD_ADDR |
+					    OPTION_MPTCP_RM_ADDR |
+					    OPTION_MPTCP_PRIO |
+					    OPTION_MPTCP_FASTCLOSE |
+					    OPTION_MPTCP_FAIL)) != 0)
+			break;
+
 		pr_debug("DSS\n");
 		ptr++;
 
@@ -188,8 +209,14 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 		 * RFC 8684 Section 3.3.0 checks later in subflow_data_ready
 		 */
 		if (opsize != expected_opsize &&
-		    opsize != expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM)
+		    opsize != expected_opsize + TCPOLEN_MPTCP_DSS_CHECKSUM) {
+			mp_opt->dsn64 = 0;
+			mp_opt->use_map = 0;
+			mp_opt->ack64 = 0;
+			mp_opt->use_ack = 0;
+			mp_opt->data_fin = 0;
 			break;
+		}
 
 		mp_opt->suboptions |= OPTION_MPTCP_DSS;
 		if (mp_opt->use_ack) {
@@ -234,6 +261,12 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 		break;
 
 	case MPTCPOPT_ADD_ADDR:
+		/* Can be used with a restricted number of other options */
+		if ((mp_opt->suboptions & ~(OPTIONS_MPTCP_DSS |
+					    OPTION_MPTCP_RM_ADDR |
+					    OPTION_MPTCP_PRIO)) != 0)
+			break;
+
 		mp_opt->echo = (*ptr++) & MPTCP_ADDR_ECHO;
 		if (!mp_opt->echo) {
 			if (opsize == TCPOLEN_MPTCP_ADD_ADDR ||
@@ -293,6 +326,14 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 		break;
 
 	case MPTCPOPT_RM_ADDR:
+		/* Can be used with a restricted number of other options */
+		if ((mp_opt->suboptions & ~(OPTION_MPTCP_MPC_ACK |
+					    OPTIONS_MPTCP_MPJ |
+					    OPTIONS_MPTCP_DSS |
+					    OPTION_MPTCP_ADD_ADDR |
+					    OPTION_MPTCP_PRIO)) != 0)
+			break;
+
 		if (opsize < TCPOLEN_MPTCP_RM_ADDR_BASE + 1 ||
 		    opsize > TCPOLEN_MPTCP_RM_ADDR_BASE + MPTCP_RM_IDS_MAX)
 			break;
@@ -307,6 +348,13 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 		break;
 
 	case MPTCPOPT_MP_PRIO:
+		/* Can be used with a restricted number of other options */
+		if ((mp_opt->suboptions & ~(OPTIONS_MPTCP_MPJ |
+					    OPTIONS_MPTCP_DSS |
+					    OPTION_MPTCP_ADD_ADDR |
+					    OPTION_MPTCP_RM_ADDR)) != 0)
+			break;
+
 		if (opsize != TCPOLEN_MPTCP_PRIO)
 			break;
 
@@ -316,6 +364,11 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 		break;
 
 	case MPTCPOPT_MP_FASTCLOSE:
+		/* Can be used with a restricted number of other options */
+		if ((mp_opt->suboptions & ~(OPTIONS_MPTCP_DSS |
+					    OPTION_MPTCP_RST)) != 0)
+			break;
+
 		if (opsize != TCPOLEN_MPTCP_FASTCLOSE)
 			break;
 
@@ -327,6 +380,11 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 		break;
 
 	case MPTCPOPT_RST:
+		/* Can be used with a restricted number of other options */
+		if ((mp_opt->suboptions & ~(OPTION_MPTCP_FAIL |
+					    OPTION_MPTCP_FASTCLOSE)) != 0)
+			break;
+
 		if (opsize != TCPOLEN_MPTCP_RST)
 			break;
 
@@ -342,6 +400,11 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 		break;
 
 	case MPTCPOPT_MP_FAIL:
+		/* Can be used with a restricted number of other options */
+		if ((mp_opt->suboptions & ~(OPTIONS_MPTCP_DSS |
+					    OPTION_MPTCP_RST)) != 0)
+			break;
+
 		if (opsize != TCPOLEN_MPTCP_FAIL)
 			break;
 
@@ -1400,7 +1463,7 @@ void mptcp_write_options(struct tcphdr *th, __be32 *ptr, struct tcp_sock *tp,
 	 *  RM   |  C   |  C   |  C   |  P   |------|------|------|------|
 	 *  PRIO |  X   |  C   |  C   |  C   |  C   |------|------|------|
 	 *  FAIL |  X   |  X   |  C   |  X   |  X   |  X   |------|------|
-	 *  FC   |  X   |  X   |  X   |  X   |  X   |  X   |  X   |------|
+	 *  FC   |  X   |  X   |  P   |  X   |  X   |  X   |  X   |------|
 	 *  RST  |  X   |  X   |  X   |  X   |  X   |  X   |  O   |  O   |
 	 * ------|------|------|------|------|------|------|------|------|
 	 *
diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c
index 6afd39aea110..64a1236aabee 100644
--- a/net/mptcp/pm.c
+++ b/net/mptcp/pm.c
@@ -380,6 +380,7 @@ static void mptcp_pm_add_addr_timer(struct timer_list *timer)
 	struct mptcp_sock *msk = entry->sock;
 	struct sock *sk = (struct sock *)msk;
 	unsigned int timeout = 0;
+	bool retransmit;
 
 	pr_debug("msk=%p\n", msk);
 
@@ -412,14 +413,15 @@ static void mptcp_pm_add_addr_timer(struct timer_list *timer)
 		entry->retrans_times++;
 	}
 
-	if (entry->retrans_times < ADD_ADDR_RETRANS_MAX)
+	retransmit = entry->retrans_times < ADD_ADDR_RETRANS_MAX;
+	if (retransmit)
 		timeout <<= entry->retrans_times;
 	else
 		timeout = 0;
 
 	spin_unlock_bh(&msk->pm.lock);
 
-	if (entry->retrans_times == ADD_ADDR_RETRANS_MAX)
+	if (!retransmit)
 		mptcp_pm_subflow_established(msk);
 
 out:
@@ -441,6 +443,9 @@ bool mptcp_pm_announced_alloc(struct mptcp_sock *msk,
 
 	lockdep_assert_held(&msk->pm.lock);
 
+	if (msk->pm.status & BIT(MPTCP_PM_DESTROYING))
+		return false;
+
 	add_entry = mptcp_pm_announced_lookup(msk, addr);
 	if (add_entry) {
 		if (WARN_ON_ONCE(mptcp_pm_is_kernel(msk)))
@@ -1143,10 +1148,16 @@ void mptcp_pm_worker(struct mptcp_sock *msk)
 
 void mptcp_pm_destroy(struct mptcp_sock *msk)
 {
+	spin_lock_bh(&msk->pm.lock);
+	msk->pm.status |= BIT(MPTCP_PM_DESTROYING);
+	spin_unlock_bh(&msk->pm.lock);
+
 	mptcp_pm_free_announced_list(msk);
 
-	if (mptcp_pm_is_userspace(msk))
-		mptcp_userspace_pm_free_local_addr_list(msk);
+	/* Free the userspace local address list unconditionally: the socket
+	 * can be reused (mptcp_disconnect()) and re-selected to a different PM
+	 */
+	mptcp_userspace_pm_free_local_addr_list(msk);
 }
 
 void mptcp_pm_data_reset(struct mptcp_sock *msk)
diff --git a/net/mptcp/pm_userspace.c b/net/mptcp/pm_userspace.c
index 945aa5afc2dd..2203cc2d2748 100644
--- a/net/mptcp/pm_userspace.c
+++ b/net/mptcp/pm_userspace.c
@@ -54,6 +54,10 @@ static int mptcp_userspace_pm_append_new_local_addr(struct mptcp_sock *msk,
 	bitmap_zero(id_bitmap, MPTCP_PM_MAX_ADDR_ID + 1);
 
 	spin_lock_bh(&msk->pm.lock);
+	if (msk->pm.status & BIT(MPTCP_PM_DESTROYING)) {
+		ret = -EINVAL;
+		goto append_err;
+	}
 	mptcp_for_each_userspace_pm_addr(msk, e) {
 		addr_match = mptcp_addresses_equal(&e->addr, &entry->addr, true);
 		if (addr_match && entry->addr.id == 0 && needs_id)
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index ca644ec53eed..7c8180d8d5ef 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -149,6 +149,12 @@ struct sock *__mptcp_nmpc_sk(struct mptcp_sock *msk)
 
 static void mptcp_drop(struct sock *sk, struct sk_buff *skb)
 {
+	/* The skb forward memory was already transferred to sk by
+	 * mptcp_borrow_fwdmem(), even before setting the destructor.
+	 */
+	if (!skb->destructor)
+		sk_mem_reclaim(sk);
+
 	sk_drops_skbadd(sk, skb);
 	__kfree_skb(skb);
 }
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 4a2d40cd7b13..1b80f2d6ec5a 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -37,6 +37,7 @@
 				 OPTION_MPTCP_MPC_ACK)
 #define OPTIONS_MPTCP_MPJ	(OPTION_MPTCP_MPJ_SYN | OPTION_MPTCP_MPJ_SYNACK | \
 				 OPTION_MPTCP_MPJ_ACK)
+#define OPTIONS_MPTCP_DSS	(OPTION_MPTCP_DSS | OPTION_MPTCP_CSUMREQD)
 
 /* MPTCP option subtypes */
 #define MPTCPOPT_MP_CAPABLE	0
@@ -189,9 +190,10 @@ enum mptcp_pm_status {
 	MPTCP_PM_ESTABLISHED,
 	MPTCP_PM_SUBFLOW_ESTABLISHED,
 	MPTCP_PM_ALREADY_ESTABLISHED,	/* persistent status, set after ESTABLISHED event */
-	MPTCP_PM_MPC_ENDPOINT_ACCOUNTED /* persistent status, set after MPC local address is
-					 * accounted int id_avail_bitmap
-					 */
+	MPTCP_PM_MPC_ENDPOINT_ACCOUNTED, /* persistent status, set after MPC local address is
+					  * accounted int id_avail_bitmap
+					  */
+	MPTCP_PM_DESTROYING,		/* To fence out PM list allocs */
 };
 
 enum mptcp_pm_type {
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 8e386899ceb9..e1f20ff8fdb4 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -174,8 +174,6 @@ static int subflow_check_req(struct request_sock *req,
 
 		if (unlikely(listener->pm_listener))
 			return subflow_reset_req_endp(req, skb);
-		if (opt_mp_join)
-			return 0;
 	} else if (opt_mp_join) {
 		SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINSYNRX);
 
@@ -277,9 +275,6 @@ int mptcp_subflow_init_cookie_req(struct request_sock *req,
 
 	opt_mp_capable = !!(mp_opt.suboptions & OPTION_MPTCP_MPC_ACK);
 	opt_mp_join = !!(mp_opt.suboptions & OPTION_MPTCP_MPJ_ACK);
-	if (opt_mp_capable && opt_mp_join)
-		return -EINVAL;
-
 	if (opt_mp_capable && listener->request_mptcp) {
 		if (mp_opt.sndr_key == 0)
 			return -EINVAL;
diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index c0aeffd5cb71..7dc91fac4917 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -584,7 +584,7 @@ check_transfer()
 		mv "$tmpfile" "$out"
 		tmpfile=""
 	fi
-	cmp -l "$in" "$out" | while read -r i a b; do
+	while read -r i a b; do
 		local sum=$((0${a} + 0${b}))
 		if [ $check_invert -eq 0 ] || [ $sum -ne $((0xff)) ]; then
 			fail_test "$what does not match (in, out):"
@@ -595,7 +595,7 @@ check_transfer()
 		else
 			print_info "$what has inverted byte at ${i}"
 		fi
-	done
+	done < <(cmp -l "$in" "$out")
 
 	return 0
 }