diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
index 5c12761cbc0e..07198beb3d80 100644
--- a/include/net/bluetooth/hci.h
+++ b/include/net/bluetooth/hci.h
@@ -1666,6 +1666,15 @@ struct hci_cp_le_set_event_mask {
 	__u8     mask[8];
 } __packed;
 
+/* BLUETOOTH CORE SPECIFICATION Version 5.4 | Vol 4, Part E
+ * 7.8.2 LE Read Buffer Size command
+ * MAX_LE_MTU is 0xffff.
+ * 0 is also valid. It means that no dedicated LE Buffer exists.
+ * It should use the HCI_Read_Buffer_Size command and mtu is shared
+ * between BR/EDR and LE.
+ */
+#define HCI_MIN_LE_MTU 0x001b
+
 #define HCI_OP_LE_READ_BUFFER_SIZE	0x2002
 struct hci_rp_le_read_buffer_size {
 	__u8     status;
diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
index e8f581f3f3ce..b1c8489ff93e 100644
--- a/include/net/bluetooth/hci_core.h
+++ b/include/net/bluetooth/hci_core.h
@@ -706,6 +706,7 @@ struct hci_conn {
 	__u16		handle;
 	__u16		sync_handle;
 	__u16		state;
+	__u16		mtu;
 	__u8		mode;
 	__u8		type;
 	__u8		role;
diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index 05346250f719..6ab404dda794 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -909,11 +909,37 @@ struct hci_conn *hci_conn_add(struct hci_dev *hdev, int type, bdaddr_t *dst,
 {
 	struct hci_conn *conn;
 
+	switch (type) {
+	case ACL_LINK:
+		if (!hdev->acl_mtu)
+			return ERR_PTR(-ECONNREFUSED);
+		break;
+	case ISO_LINK:
+		if (hdev->iso_mtu)
+			/* Dedicated ISO Buffer exists */
+			break;
+		fallthrough;
+	case LE_LINK:
+		if (hdev->le_mtu && hdev->le_mtu < HCI_MIN_LE_MTU)
+			return ERR_PTR(-ECONNREFUSED);
+		if (!hdev->le_mtu && hdev->acl_mtu < HCI_MIN_LE_MTU)
+			return ERR_PTR(-ECONNREFUSED);
+		break;
+	case SCO_LINK:
+	case ESCO_LINK:
+		if (!hdev->sco_pkts)
+			/* Controller does not support SCO or eSCO over HCI */
+			return ERR_PTR(-ECONNREFUSED);
+		break;
+	default:
+		return ERR_PTR(-ECONNREFUSED);
+	}
+
 	bt_dev_dbg(hdev, "dst %pMR handle 0x%4.4x", dst, handle);
 
 	conn = kzalloc(sizeof(*conn), GFP_KERNEL);
 	if (!conn)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	bacpy(&conn->dst, dst);
 	bacpy(&conn->src, &hdev->bdaddr);
@@ -944,10 +970,12 @@ struct hci_conn *hci_conn_add(struct hci_dev *hdev, int type, bdaddr_t *dst,
 	switch (type) {
 	case ACL_LINK:
 		conn->pkt_type = hdev->pkt_type & ACL_PTYPE_MASK;
+		conn->mtu = hdev->acl_mtu;
 		break;
 	case LE_LINK:
 		/* conn->src should reflect the local identity address */
 		hci_copy_identity_address(hdev, &conn->src, &conn->src_type);
+		conn->mtu = hdev->le_mtu ? hdev->le_mtu : hdev->acl_mtu;
 		break;
 	case ISO_LINK:
 		/* conn->src should reflect the local identity address */
@@ -959,6 +987,8 @@ struct hci_conn *hci_conn_add(struct hci_dev *hdev, int type, bdaddr_t *dst,
 		else if (conn->role == HCI_ROLE_MASTER)
 			conn->cleanup = cis_cleanup;
 
+		conn->mtu = hdev->iso_mtu ? hdev->iso_mtu :
+			    hdev->le_mtu ? hdev->le_mtu : hdev->acl_mtu;
 		break;
 	case SCO_LINK:
 		if (lmp_esco_capable(hdev))
@@ -966,9 +996,12 @@ struct hci_conn *hci_conn_add(struct hci_dev *hdev, int type, bdaddr_t *dst,
 					(hdev->esco_type & EDR_ESCO_MASK);
 		else
 			conn->pkt_type = hdev->pkt_type & SCO_PTYPE_MASK;
+
+		conn->mtu = hdev->sco_mtu;
 		break;
 	case ESCO_LINK:
 		conn->pkt_type = hdev->esco_type & ~EDR_ESCO_MASK;
+		conn->mtu = hdev->sco_mtu;
 		break;
 	}
 
@@ -1011,7 +1044,7 @@ struct hci_conn *hci_conn_add_unset(struct hci_dev *hdev, int type,
 
 	handle = hci_conn_hash_alloc_unset(hdev);
 	if (unlikely(handle < 0))
-		return NULL;
+		return ERR_PTR(-ECONNREFUSED);
 
 	return hci_conn_add(hdev, type, dst, role, handle);
 }
@@ -1317,8 +1350,8 @@ struct hci_conn *hci_connect_le(struct hci_dev *hdev, bdaddr_t *dst,
 		bacpy(&conn->dst, dst);
 	} else {
 		conn = hci_conn_add_unset(hdev, LE_LINK, dst, role);
-		if (!conn)
-			return ERR_PTR(-ENOMEM);
+		if (IS_ERR(conn))
+			return conn;
 		hci_conn_hold(conn);
 		conn->pending_sec_level = sec_level;
 	}
@@ -1494,8 +1527,8 @@ static struct hci_conn *hci_add_bis(struct hci_dev *hdev, bdaddr_t *dst,
 		return ERR_PTR(-EADDRINUSE);
 
 	conn = hci_conn_add_unset(hdev, ISO_LINK, dst, HCI_ROLE_MASTER);
-	if (!conn)
-		return ERR_PTR(-ENOMEM);
+	if (IS_ERR(conn))
+		return conn;
 
 	conn->state = BT_CONNECT;
 
@@ -1538,8 +1571,8 @@ struct hci_conn *hci_connect_le_scan(struct hci_dev *hdev, bdaddr_t *dst,
 	BT_DBG("requesting refresh of dst_addr");
 
 	conn = hci_conn_add_unset(hdev, LE_LINK, dst, HCI_ROLE_MASTER);
-	if (!conn)
-		return ERR_PTR(-ENOMEM);
+	if (IS_ERR(conn))
+		return conn;
 
 	if (hci_explicit_conn_params_set(hdev, dst, dst_type) < 0) {
 		hci_conn_del(conn);
@@ -1586,8 +1619,8 @@ struct hci_conn *hci_connect_acl(struct hci_dev *hdev, bdaddr_t *dst,
 	acl = hci_conn_hash_lookup_ba(hdev, ACL_LINK, dst);
 	if (!acl) {
 		acl = hci_conn_add_unset(hdev, ACL_LINK, dst, HCI_ROLE_MASTER);
-		if (!acl)
-			return ERR_PTR(-ENOMEM);
+		if (IS_ERR(acl))
+			return acl;
 	}
 
 	hci_conn_hold(acl);
@@ -1655,9 +1688,9 @@ struct hci_conn *hci_connect_sco(struct hci_dev *hdev, int type, bdaddr_t *dst,
 	sco = hci_conn_hash_lookup_ba(hdev, type, dst);
 	if (!sco) {
 		sco = hci_conn_add_unset(hdev, type, dst, HCI_ROLE_MASTER);
-		if (!sco) {
+		if (IS_ERR(sco)) {
 			hci_conn_drop(acl);
-			return ERR_PTR(-ENOMEM);
+			return sco;
 		}
 	}
 
@@ -1847,8 +1880,8 @@ struct hci_conn *hci_bind_cis(struct hci_dev *hdev, bdaddr_t *dst,
 				       qos->ucast.cis);
 	if (!cis) {
 		cis = hci_conn_add_unset(hdev, ISO_LINK, dst, HCI_ROLE_MASTER);
-		if (!cis)
-			return ERR_PTR(-ENOMEM);
+		if (IS_ERR(cis))
+			return cis;
 		cis->cleanup = cis_cleanup;
 		cis->dst_type = dst_type;
 		cis->iso_qos.ucast.cig = BT_ISO_QOS_CIG_UNSET;
@@ -1983,14 +2016,8 @@ static void hci_iso_qos_setup(struct hci_dev *hdev, struct hci_conn *conn,
 			      struct bt_iso_io_qos *qos, __u8 phy)
 {
 	/* Only set MTU if PHY is enabled */
-	if (!qos->sdu && qos->phy) {
-		if (hdev->iso_mtu > 0)
-			qos->sdu = hdev->iso_mtu;
-		else if (hdev->le_mtu > 0)
-			qos->sdu = hdev->le_mtu;
-		else
-			qos->sdu = hdev->acl_mtu;
-	}
+	if (!qos->sdu && qos->phy)
+		qos->sdu = conn->mtu;
 
 	/* Use the same PHY as ACL if set to any */
 	if (qos->phy == BT_ISO_PHY_ANY)
@@ -2071,8 +2098,8 @@ struct hci_conn *hci_pa_create_sync(struct hci_dev *hdev, bdaddr_t *dst,
 		return ERR_PTR(-EBUSY);
 
 	conn = hci_conn_add_unset(hdev, ISO_LINK, dst, HCI_ROLE_SLAVE);
-	if (!conn)
-		return ERR_PTR(-ENOMEM);
+	if (IS_ERR(conn))
+		return conn;
 
 	conn->iso_qos = *qos;
 	conn->state = BT_LISTEN;
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index d72d238c1656..4de8f0dc1a52 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -954,6 +954,9 @@ static u8 hci_cc_read_buffer_size(struct hci_dev *hdev, void *data,
 	BT_DBG("%s acl mtu %d:%d sco mtu %d:%d", hdev->name, hdev->acl_mtu,
 	       hdev->acl_pkts, hdev->sco_mtu, hdev->sco_pkts);
 
+	if (!hdev->acl_mtu || !hdev->acl_pkts)
+		return HCI_ERROR_INVALID_PARAMETERS;
+
 	return rp->status;
 }
 
@@ -1263,6 +1266,9 @@ static u8 hci_cc_le_read_buffer_size(struct hci_dev *hdev, void *data,
 
 	BT_DBG("%s le mtu %d:%d", hdev->name, hdev->le_mtu, hdev->le_pkts);
 
+	if (hdev->le_mtu && hdev->le_mtu < HCI_MIN_LE_MTU)
+		return HCI_ERROR_INVALID_PARAMETERS;
+
 	return rp->status;
 }
 
@@ -2342,8 +2348,8 @@ static void hci_cs_create_conn(struct hci_dev *hdev, __u8 status)
 		if (!conn) {
 			conn = hci_conn_add_unset(hdev, ACL_LINK, &cp->bdaddr,
 						  HCI_ROLE_MASTER);
-			if (!conn)
-				bt_dev_err(hdev, "no memory for new connection");
+			if (IS_ERR(conn))
+				bt_dev_err(hdev, "connection err: %ld", PTR_ERR(conn));
 		}
 	}
 
@@ -3154,8 +3160,8 @@ static void hci_conn_complete_evt(struct hci_dev *hdev, void *data,
 						      BDADDR_BREDR)) {
 			conn = hci_conn_add_unset(hdev, ev->link_type,
 						  &ev->bdaddr, HCI_ROLE_SLAVE);
-			if (!conn) {
-				bt_dev_err(hdev, "no memory for new conn");
+			if (IS_ERR(conn)) {
+				bt_dev_err(hdev, "connection err: %ld", PTR_ERR(conn));
 				goto unlock;
 			}
 		} else {
@@ -3343,8 +3349,8 @@ static void hci_conn_request_evt(struct hci_dev *hdev, void *data,
 	if (!conn) {
 		conn = hci_conn_add_unset(hdev, ev->link_type, &ev->bdaddr,
 					  HCI_ROLE_SLAVE);
-		if (!conn) {
-			bt_dev_err(hdev, "no memory for new connection");
+		if (IS_ERR(conn)) {
+			bt_dev_err(hdev, "connection err: %ld", PTR_ERR(conn));
 			goto unlock;
 		}
 	}
@@ -3821,6 +3827,9 @@ static u8 hci_cc_le_read_buffer_size_v2(struct hci_dev *hdev, void *data,
 	BT_DBG("%s acl mtu %d:%d iso mtu %d:%d", hdev->name, hdev->acl_mtu,
 	       hdev->acl_pkts, hdev->iso_mtu, hdev->iso_pkts);
 
+	if (hdev->le_mtu && hdev->le_mtu < HCI_MIN_LE_MTU)
+		return HCI_ERROR_INVALID_PARAMETERS;
+
 	return rp->status;
 }
 
@@ -5768,8 +5777,8 @@ static void le_conn_complete_evt(struct hci_dev *hdev, u8 status,
 			goto unlock;
 
 		conn = hci_conn_add_unset(hdev, LE_LINK, bdaddr, role);
-		if (!conn) {
-			bt_dev_err(hdev, "no memory for new connection");
+		if (IS_ERR(conn)) {
+			bt_dev_err(hdev, "connection err: %ld", PTR_ERR(conn));
 			goto unlock;
 		}
 
@@ -6898,7 +6907,7 @@ static void hci_le_cis_req_evt(struct hci_dev *hdev, void *data,
 	if (!cis) {
 		cis = hci_conn_add(hdev, ISO_LINK, &acl->dst, HCI_ROLE_SLAVE,
 				   cis_handle);
-		if (!cis) {
+		if (IS_ERR(cis)) {
 			hci_le_reject_cis(hdev, ev->cis_handle);
 			goto unlock;
 		}
@@ -7007,7 +7016,7 @@ static void hci_le_big_sync_established_evt(struct hci_dev *hdev, void *data,
 		if (!bis) {
 			bis = hci_conn_add(hdev, ISO_LINK, BDADDR_ANY,
 					   HCI_ROLE_SLAVE, handle);
-			if (!bis)
+			if (IS_ERR(bis))
 				continue;
 		}
 
@@ -7079,7 +7088,7 @@ static void hci_le_big_info_adv_report_evt(struct hci_dev *hdev, void *data,
 	pa_sync = hci_conn_add_unset(hdev, ISO_LINK, BDADDR_ANY,
 				     HCI_ROLE_SLAVE);
 
-	if (!pa_sync)
+	if (IS_ERR(pa_sync))
 		goto unlock;
 
 	pa_sync->sync_handle = le16_to_cpu(ev->sync_handle);
diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c
index ef0cc80b4c0c..6bed4aa8291d 100644
--- a/net/bluetooth/iso.c
+++ b/net/bluetooth/iso.c
@@ -1285,7 +1285,7 @@ static int iso_sock_sendmsg(struct socket *sock, struct msghdr *msg,
 		return -ENOTCONN;
 	}
 
-	mtu = iso_pi(sk)->conn->hcon->hdev->iso_mtu;
+	mtu = iso_pi(sk)->conn->hcon->mtu;
 
 	release_sock(sk);
 
diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 9223b1a698e3..3f7a82f10fe9 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -6241,7 +6241,7 @@ static int l2cap_finish_move(struct l2cap_chan *chan)
 	BT_DBG("chan %p", chan);
 
 	chan->rx_state = L2CAP_RX_STATE_RECV;
-	chan->conn->mtu = chan->conn->hcon->hdev->acl_mtu;
+	chan->conn->mtu = chan->conn->hcon->mtu;
 
 	return l2cap_resegment(chan);
 }
@@ -6308,7 +6308,7 @@ static int l2cap_rx_state_wait_f(struct l2cap_chan *chan,
 	 */
 	chan->next_tx_seq = control->reqseq;
 	chan->unacked_frames = 0;
-	chan->conn->mtu = chan->conn->hcon->hdev->acl_mtu;
+	chan->conn->mtu = chan->conn->hcon->mtu;
 
 	err = l2cap_resegment(chan);
 
@@ -6848,18 +6848,7 @@ static struct l2cap_conn *l2cap_conn_add(struct hci_conn *hcon)
 
 	BT_DBG("hcon %p conn %p hchan %p", hcon, conn, hchan);
 
-	switch (hcon->type) {
-	case LE_LINK:
-		if (hcon->hdev->le_mtu) {
-			conn->mtu = hcon->hdev->le_mtu;
-			break;
-		}
-		fallthrough;
-	default:
-		conn->mtu = hcon->hdev->acl_mtu;
-		break;
-	}
-
+	conn->mtu = hcon->mtu;
 	conn->feat_mask = 0;
 
 	conn->local_fixed_chan = L2CAP_FC_SIG_BREDR | L2CAP_FC_CONNLESS;
diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c
index e0ad30862ee4..71d36582d4ef 100644
--- a/net/bluetooth/sco.c
+++ b/net/bluetooth/sco.c
@@ -126,7 +126,6 @@ static void sco_sock_clear_timer(struct sock *sk)
 /* ---- SCO connections ---- */
 static struct sco_conn *sco_conn_add(struct hci_conn *hcon)
 {
-	struct hci_dev *hdev = hcon->hdev;
 	struct sco_conn *conn = hcon->sco_data;
 
 	if (conn) {
@@ -144,9 +143,10 @@ static struct sco_conn *sco_conn_add(struct hci_conn *hcon)
 
 	hcon->sco_data = conn;
 	conn->hcon = hcon;
+	conn->mtu = hcon->mtu;
 
-	if (hdev->sco_mtu > 0)
-		conn->mtu = hdev->sco_mtu;
+	if (hcon->mtu > 0)
+		conn->mtu = hcon->mtu;
 	else
 		conn->mtu = 60;