Syzbot reported a corrupted list in kobject_add_internal [1]. This happens when multiple HCI_EV_SYNC_CONN_COMPLETE event packets with status 0 are sent for the same HCI connection. This causes us to register the device more than once which corrupts the kset list. As this is forbidden behavior, we add a check for whether we're trying to process the same HCI_EV_SYNC_CONN_COMPLETE event multiple times for one connection. If that's the case, the event is invalid, so we report an error that the device is misbehaving, and ignore the packet. Link: https://syzkaller.appspot.com/bug?extid=66264bf2fd0476be7e6c [1] Reported-by: syzbot+66264bf2fd0476be7e6c@xxxxxxxxxxxxxxxxxxxxxxxxx Tested-by: syzbot+66264bf2fd0476be7e6c@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@xxxxxxxxx> --- v1 -> v2: - Added more comments to explain the reasoning behind the new check, and a bt_dev_err message upon detecting the invalid event. As suggested by Marcel Holtmann. net/bluetooth/hci_event.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c index 016b2999f219..a6df4f9d2c23 100644 --- a/net/bluetooth/hci_event.c +++ b/net/bluetooth/hci_event.c @@ -4373,6 +4373,22 @@ static void hci_sync_conn_complete_evt(struct hci_dev *hdev, switch (ev->status) { case 0x00: + /* The synchronous connection complete event should only be + * sent once per new connection. Receiving a successful + * complete event when the connection status is already + * BT_CONNECTED means that the device is misbehaving and sent + * multiple complete event packets for the same new connection. + * + * Registering the device more than once can corrupt kernel + * memory, hence upon detecting this invalid event, we report + * an error and ignore the packet. + */ + if (conn->state == BT_CONNECTED) { + bt_dev_err(hdev, + "received multiple HCI_EV_SYNC_CONN_COMPLETE events with status 0 for conn %p", + conn); + goto unlock; + } conn->handle = __le16_to_cpu(ev->handle); conn->state = BT_CONNECTED; conn->type = ev->link_type; -- 2.25.1
