Hi Luiz, On 21.01.22 22:31, Luiz Augusto von Dentz wrote: > Hi Sönke, > > On Fri, Jan 21, 2022 at 10:22 AM Sönke Huster <soenke.huster@xxxxxxxxx> wrote: >> >> I just noticed that just checking for handle does not work, as obviously 0x0 could also be a handle value and therefore it can't be distinguished, whether it is not set yet or it is 0x0. > > Yep, we should probably check its state, check for state != BT_OPEN > since that is what hci_conn_add initialize the state. > I thought there are more valid connection states for the first HCI_CONNECTION_COMPLETE event, as it also occurs e.g. after an HCI_Create_Connection command, see Core 5.3 p.2170: > This event also indicates to the Host which issued the HCI_Create_Connection, HCI_Accept_- > Connection_Request, or HCI_Reject_Connection_Request command, and > then received an HCI_Command_Status event, if the issued command failed or > was successful. For example in hci_conn.c hci_acl_create_connection (which triggers a HCI_Create_Connection command as far as I understand), the state of the connection is changed to BT_CONNECT or BT_CONNECT2. But as I am quite new in the (Linux) Bluetooth world, I might have a wrong understanding of that. >> On 21.01.22 18:36, Soenke Huster wrote: >>> When a HCI_CONNECTION_COMPLETE event is received multiple times >>> for the same handle, the device is registered multiple times which leads >>> to memory corruptions. Therefore, consequent events for a single >>> connection are ignored. >>> >>> The conn->state can hold different values so conn->handle is >>> checked to detect whether a connection is already set up. >>> >>> Buglink: https://bugzilla.kernel.org/show_bug.cgi?id=215497 >>> Signed-off-by: Soenke Huster <soenke.huster@xxxxxxxxx> >>> --- >>> This fixes the referenced bug and several use-after-free issues I discovered. >>> I tagged it as RFC, as I am not 100% sure if checking the existence of the >>> handle is the correct approach, but to the best of my knowledge it must be >>> set for the first time in this function for valid connections of this event, >>> therefore it should be fine. >>> >>> net/bluetooth/hci_event.c | 11 +++++++++++ >>> 1 file changed, 11 insertions(+) >>> >>> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c >>> index 681c623aa380..71ccb12c928d 100644 >>> --- a/net/bluetooth/hci_event.c >>> +++ b/net/bluetooth/hci_event.c >>> @@ -3106,6 +3106,17 @@ static void hci_conn_complete_evt(struct hci_dev *hdev, void *data, >>> } >>> } >>> >>> + /* The HCI_Connection_Complete event is only sent once per connection. >>> + * Processing it more than once per connection can corrupt kernel memory. >>> + * >>> + * As the connection handle is set here for the first time, it indicates >>> + * whether the connection is already set up. >>> + */ >>> + if (conn->handle) { >>> + bt_dev_err(hdev, "Ignoring HCI_Connection_Complete for existing connection"); >>> + goto unlock; >>> + } >>> + >>> if (!ev->status) { >>> conn->handle = __le16_to_cpu(ev->handle); >>> > > > Best Sönke
