[PATCH] net: bluetooth: fix consistent connection failure caused by the loss of HCI_Connection_Complete event

[Xin-Yu Liu <by2239112@buaa.edu.cn>]

During a connection attempt, if the HCI_Connection_Complete event
is lost and not received by the Host, it will result in
a connection failure.

In that process, the hci_conn, the handle of which is still
HCI_CONN_HANDLE_UNSET, will not be removed from the conn_hash
as it would during a regular disconnection opration.
Consequently, when an ACL connection is initiated for the same device,
the hci_conn is found in hash_conn based on "ba", with its state remaining
BT_CONNECT. Then the Host will send an HCI_Create_Connection_Cancel 
command, which will result in subsequent Bluetooth connections 
for the same device consistently failing.

In order to solve the potential bug, if the hci_conn's state is
BT_CONNECT and handle is HCI_CONN_HANDLE_UNSET, remove this hci_conn
from conn_hash. This adjustment could potentially help ensure that the
specific conn is cleaned up at the appropriate times, then the subsequent
connection for the same device will no longer experience failures.

Signed-off-by: Xin-Yu Liu <by2239112@buaa.edu.cn>
---
 net/bluetooth/hci_conn.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index 76222565e..219c62579 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -2886,6 +2886,10 @@ int hci_abort_conn(struct hci_conn *conn, u8 reason)
 		} else if (conn->type == ACL_LINK) {
 			if (conn->hdev->hci_ver < BLUETOOTH_VER_1_2)
 				break;
+			if (conn->state == HCI_CONN_HANDLE_UNSET) {
+				hci_conn_cleanup(conn);
+				break;
+			}
 			r = hci_send_cmd(conn->hdev,
 					 HCI_OP_CREATE_CONN_CANCEL,
 					 6, &conn->dst);
-- 
2.25.1