Bluetooth: L2CAP: Fix missing key size check for L2CAP_LE_CONN_REQ

This adds a check for encryption key size upon receiving
L2CAP_LE_CONN_REQ which is required by L2CAP/LE/CFC/BV-15-C which
expects L2CAP_CR_LE_BAD_KEY_SIZE.

Link: https://lore.kernel.org/linux-bluetooth/5782243.rdbgypaU67@n9w6sw14/
Fixes: 27e2d4c ("Bluetooth: Add basic LE L2CAP connect request receiving support")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Tested-by: Christian Eggers <ceggers@arri.de>

Author: Vudentz

net/bluetooth/l2cap_core.c

@@ -4916,6 +4916,13 @@ static int l2cap_le_connect_req(struct l2cap_conn *conn,
 		goto response_unlock;
 	}
 
+	/* Check if Key Size is sufficient for the security level */
+	if (!l2cap_check_enc_key_size(conn->hcon, pchan)) {
+		result = L2CAP_CR_LE_BAD_KEY_SIZE;
+		chan = NULL;
+		goto response_unlock;
+	}
+
 	/* Check for valid dynamic CID range */
 	if (scid < L2CAP_CID_DYN_START || scid > L2CAP_CID_LE_DYN_END) {
 		result = L2CAP_CR_LE_INVALID_SCID;