Bluetooth: skip invalid hci_sync_conn_complete_evt

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
Reported-by: syzbot+66264bf2fd0476be7e6c@syzkaller.appspotmail.com
Tested-by: syzbot+66264bf2fd0476be7e6c@syzkaller.appspotmail.com
Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 1c30182..ea7fc09 100644 (file)
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -4382,6 +4382,21 @@ 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, "Ignoring connect complete event for existing connection");
+                       goto unlock;
+               }
+
                conn->handle = __le16_to_cpu(ev->handle);
                conn->state  = BT_CONNECTED;
                conn->type   = ev->link_type;