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SubjectRe: [PATCH] Bluetooth: skip invalid hci_sync_conn_complete_evt
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On 22/7/21 10:39 pm, Marcel Holtmann wrote:
> Hi Desmond,
>
>> 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.
>
> and that is actually forbidden by the spec. So we need to complain loudly that such a device is misbehaving.
>
>> To fix this, in hci_sync_conn_complete_evt, we check 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 skip further processing and exit.
>>
>> Link: https://syzkaller.appspot.com/bug?extid=66264bf2fd0476be7e6c [1]
>> Reported-by: syzbot+66264bf2fd0476be7e6c@syzkaller.appspotmail.com
>> Tested-by: syzbot+66264bf2fd0476be7e6c@syzkaller.appspotmail.com
>> Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
>> ---
>> net/bluetooth/hci_event.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
>> index 016b2999f219..091a92338492 100644
>> --- a/net/bluetooth/hci_event.c
>> +++ b/net/bluetooth/hci_event.c
>> @@ -4373,6 +4373,8 @@ static void hci_sync_conn_complete_evt(struct hci_dev *hdev,
>>
>> switch (ev->status) {
>> case 0x00:
>> + if (conn->state == BT_CONNECTED)
>> + goto unlock; /* Already connected, event not valid */
>
> The comment has go above and be a lot more details since this is not expected behavior from valid hardware and we should add a bt_dev_err as well.
>

Hi Marcel,

Apologies for the delayed response.

Thanks for the feedback, I'll add more elaboration for the new check and
add a bt_dev_err in a v2 patch.

>> conn->handle = __le16_to_cpu(ev->handle);
>> conn->state = BT_CONNECTED;
>> conn->type = ev->link_type;
>
> Regards
>
> Marcel
>

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