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. > 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); > > -- Luiz Augusto von Dentz
