On Dec 11 2014 or thereabouts, Peter Wu wrote:
> Balance a hid_device_io_start() call with hid_device_io_stop() in the
> error path. This avoids processing of HID reports when the probe fails
> which possibly leads to invalid memory access in hid_device_probe() as
> report_enum->report_id_hash might already be freed via
> hid_close_report().
Well spotted too!
>
> hid_set_drvdata() is called before wtp_allocate, be consistent and clear
> drvdata too on the error path of wtp_allocate.
This is not strictly speaking required. We will have a dangling value in
hdev->private_data, but this should be overwritten before the next use.
Anyway, it makes sense to clean up after a failure, so the patch is
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
Cheers,
Benjamin
>
> Signed-off-by: Peter Wu <peter@xxxxxxxxxxxxx>
> ---
> Hi Andrew,
>
> There are few users of hid_device_io_start/stop, this is the first one
> to get start/stop out of sync. Should the comment of
> hid_device_io_start() be updated to ensure that hid_device_io_stop()
> gets called before probe() returns? Or should the hid-core be changed to
> handle this out-of-sync issue:
>
> if (ret) {
> if (hdev->io_started))
> down(&hdev->driver_input_lock);
> hid_close_report(hdev);
> hdev->driver = NULL;
> }
>
> Is my observation correct or not that HID reports can arrive during
> hid_close_report() when io_started == true?
>
> Kind regards,
> Peter
> ---
> drivers/hid/hid-logitech-hidpp.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
> index 4292cc3..2f420c0 100644
> --- a/drivers/hid/hid-logitech-hidpp.c
> +++ b/drivers/hid/hid-logitech-hidpp.c
> @@ -1121,7 +1121,7 @@ static int hidpp_probe(struct hid_device *hdev, const struct hid_device_id *id)
> if (hidpp->quirks & HIDPP_QUIRK_CLASS_WTP) {
> ret = wtp_allocate(hdev, id);
> if (ret)
> - return ret;
> + goto wtp_allocate_fail;
> }
>
> INIT_WORK(&hidpp->work, delayed_work_cb);
> @@ -1141,6 +1141,7 @@ static int hidpp_probe(struct hid_device *hdev, const struct hid_device_id *id)
> if (id->group != HID_GROUP_LOGITECH_DJ_DEVICE) {
> if (!connected) {
> hid_err(hdev, "Device not connected");
> + hid_device_io_stop(hdev);
> goto hid_parse_fail;
> }
>
> @@ -1186,6 +1187,7 @@ hid_hw_start_fail:
> hid_parse_fail:
> cancel_work_sync(&hidpp->work);
> mutex_destroy(&hidpp->send_mutex);
> +wtp_allocate_fail:
> hid_set_drvdata(hdev, NULL);
> return ret;
> }
> --
> 2.1.3
>
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