diff --git a/include/net/bluetooth/bluetooth.h b/include/net/bluetooth/bluetooth.h
index 4b3d0b16c185e..a647e5fabdbd6 100644
--- a/include/net/bluetooth/bluetooth.h
+++ b/include/net/bluetooth/bluetooth.h
@@ -506,8 +506,7 @@ static inline struct sk_buff *bt_skb_sendmmsg(struct sock *sk,
 
 		tmp = bt_skb_sendmsg(sk, msg, len, mtu, headroom, tailroom);
 		if (IS_ERR(tmp)) {
-			kfree_skb(skb);
-			return tmp;
+			return skb;
 		}
 
 		len -= tmp->len;
diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
index 586f69d084a2a..e336e9c1dda4f 100644
--- a/include/net/bluetooth/hci_core.h
+++ b/include/net/bluetooth/hci_core.h
@@ -1489,6 +1489,14 @@ void hci_conn_del_sysfs(struct hci_conn *conn);
 /* Extended advertising support */
 #define ext_adv_capable(dev) (((dev)->le_features[1] & HCI_LE_EXT_ADV))
 
+/* BLUETOOTH CORE SPECIFICATION Version 5.3 | Vol 4, Part E page 1789:
+ *
+ * C24: Mandatory if the LE Controller supports Connection State and either
+ * LE Feature (LL Privacy) or LE Feature (Extended Advertising) is supported
+ */
+#define use_enhanced_conn_complete(dev) (ll_privacy_capable(dev) || \
+					 ext_adv_capable(dev))
+
 /* ----- HCI protocols ----- */
 #define HCI_PROTO_DEFER             0x01
 
diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index 2b7bd3655b076..2882bc7d79d79 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -2738,6 +2738,7 @@ void hci_release_dev(struct hci_dev *hdev)
 	hci_dev_unlock(hdev);
 
 	ida_simple_remove(&hci_index_ida, hdev->id);
+	kfree_skb(hdev->sent_cmd);
 	kfree(hdev);
 }
 EXPORT_SYMBOL(hci_release_dev);
diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index 0feb68f125456..9ba2a1a7d4819 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -1841,6 +1841,7 @@ static u8 hci_update_accept_list_sync(struct hci_dev *hdev)
 	struct bdaddr_list *b, *t;
 	u8 num_entries = 0;
 	bool pend_conn, pend_report;
+	u8 filter_policy;
 	int err;
 
 	/* Pause advertising if resolving list can be used as controllers are
@@ -1927,6 +1928,8 @@ static u8 hci_update_accept_list_sync(struct hci_dev *hdev)
 		err = -EINVAL;
 
 done:
+	filter_policy = err ? 0x00 : 0x01;
+
 	/* Enable address resolution when LL Privacy is enabled. */
 	err = hci_le_set_addr_resolution_enable_sync(hdev, 0x01);
 	if (err)
@@ -1937,7 +1940,7 @@ static u8 hci_update_accept_list_sync(struct hci_dev *hdev)
 		hci_resume_advertising_sync(hdev);
 
 	/* Select filter policy to use accept list */
-	return err ? 0x00 : 0x01;
+	return filter_policy;
 }
 
 /* Returns true if an le connection is in the scanning state */
@@ -3262,10 +3265,10 @@ static int hci_le_set_event_mask_sync(struct hci_dev *hdev)
 	if (hdev->le_features[0] & HCI_LE_DATA_LEN_EXT)
 		events[0] |= 0x40;	/* LE Data Length Change */
 
-	/* If the controller supports LL Privacy feature, enable
-	 * the corresponding event.
+	/* If the controller supports LL Privacy feature or LE Extended Adv,
+	 * enable the corresponding event.
 	 */
-	if (hdev->le_features[0] & HCI_LE_LL_PRIVACY)
+	if (use_enhanced_conn_complete(hdev))
 		events[1] |= 0x02;	/* LE Enhanced Connection Complete */
 
 	/* If the controller supports Extended Scanner Filter
@@ -4106,9 +4109,9 @@ int hci_dev_close_sync(struct hci_dev *hdev)
 	hci_inquiry_cache_flush(hdev);
 	hci_pend_le_actions_clear(hdev);
 	hci_conn_hash_flush(hdev);
-	hci_dev_unlock(hdev);
-
+	/* Prevent data races on hdev->smp_data or hdev->smp_bredr_data */
 	smp_unregister(hdev);
+	hci_dev_unlock(hdev);
 
 	hci_sock_dev_event(hdev, HCI_DEV_DOWN);
 
@@ -5185,7 +5188,7 @@ int hci_le_ext_create_conn_sync(struct hci_dev *hdev, struct hci_conn *conn,
 	return __hci_cmd_sync_status_sk(hdev, HCI_OP_LE_EXT_CREATE_CONN,
 					plen, data,
 					HCI_EV_LE_ENHANCED_CONN_COMPLETE,
-					HCI_CMD_TIMEOUT, NULL);
+					conn->conn_timeout, NULL);
 }
 
 int hci_le_create_conn_sync(struct hci_dev *hdev, struct hci_conn *conn)
@@ -5270,9 +5273,18 @@ int hci_le_create_conn_sync(struct hci_dev *hdev, struct hci_conn *conn)
 	cp.min_ce_len = cpu_to_le16(0x0000);
 	cp.max_ce_len = cpu_to_le16(0x0000);
 
+	/* BLUETOOTH CORE SPECIFICATION Version 5.3 | Vol 4, Part E page 2261:
+	 *
+	 * If this event is unmasked and the HCI_LE_Connection_Complete event
+	 * is unmasked, only the HCI_LE_Enhanced_Connection_Complete event is
+	 * sent when a new connection has been created.
+	 */
 	err = __hci_cmd_sync_status_sk(hdev, HCI_OP_LE_CREATE_CONN,
-				       sizeof(cp), &cp, HCI_EV_LE_CONN_COMPLETE,
-				       HCI_CMD_TIMEOUT, NULL);
+				       sizeof(cp), &cp,
+				       use_enhanced_conn_complete(hdev) ?
+				       HCI_EV_LE_ENHANCED_CONN_COMPLETE :
+				       HCI_EV_LE_CONN_COMPLETE,
+				       conn->conn_timeout, NULL);
 
 done:
 	/* Re-enable advertising after the connection attempt is finished. */
diff --git a/net/bluetooth/mgmt_util.c b/net/bluetooth/mgmt_util.c
index edee60bbc7b46..37eef2ce55aec 100644
--- a/net/bluetooth/mgmt_util.c
+++ b/net/bluetooth/mgmt_util.c
@@ -77,11 +77,12 @@ int mgmt_send_event_skb(unsigned short channel, struct sk_buff *skb, int flag,
 {
 	struct hci_dev *hdev;
 	struct mgmt_hdr *hdr;
-	int len = skb->len;
+	int len;
 
 	if (!skb)
 		return -EINVAL;
 
+	len = skb->len;
 	hdev = bt_cb(skb)->mgmt.hdev;
 
 	/* Time stamp */