Re: [PATCH v2] Bluetooth: hci_qca: Bug fix during SSR timeout

[Abhishek Pandit-Subedi <abhishekpandit@chromium.org>]

Looks good to me.

Reviewed-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>

On Tue, Jun 9, 2020 at 8:57 AM Venkata Lakshmi Narayana Gubba
<gubbaven@codeaurora.org> wrote:
>
> Due to race conditions between qca_hw_error and qca_controller_memdump
> during SSR timeout,the same pointer is freed twice. This results in a
> double free. Now a lock is acquired before checking the stauts of SSR
> state.
>
> Fixes: d841502c79e3 ("Bluetooth: hci_qca: Collect controller memory dump during SSR")
> Signed-off-by: Venkata Lakshmi Narayana Gubba <gubbaven@codeaurora.org>
> ---
>  drivers/bluetooth/hci_qca.c | 29 +++++++++++++++++------------
>  1 file changed, 17 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
> index 28c34a1..f3fde99 100644
> --- a/drivers/bluetooth/hci_qca.c
> +++ b/drivers/bluetooth/hci_qca.c
> @@ -981,8 +981,11 @@ static void qca_controller_memdump(struct work_struct *work)
>         while ((skb = skb_dequeue(&qca->rx_memdump_q))) {
>
>                 mutex_lock(&qca->hci_memdump_lock);
> -               /* Skip processing the received packets if timeout detected. */
> -               if (qca->memdump_state == QCA_MEMDUMP_TIMEOUT) {
> +               /* Skip processing the received packets if timeout detected
> +                * or memdump collection completed.
> +                */
> +               if (qca->memdump_state == QCA_MEMDUMP_TIMEOUT ||
> +                   qca->memdump_state == QCA_MEMDUMP_COLLECTED) {
>                         mutex_unlock(&qca->hci_memdump_lock);
>                         return;
>                 }
> @@ -1483,8 +1486,6 @@ static void qca_hw_error(struct hci_dev *hdev, u8 code)
>  {
>         struct hci_uart *hu = hci_get_drvdata(hdev);
>         struct qca_data *qca = hu->priv;
> -       struct qca_memdump_data *qca_memdump = qca->qca_memdump;
> -       char *memdump_buf = NULL;
>
>         set_bit(QCA_HW_ERROR_EVENT, &qca->flags);
>         bt_dev_info(hdev, "mem_dump_status: %d", qca->memdump_state);
> @@ -1507,19 +1508,23 @@ static void qca_hw_error(struct hci_dev *hdev, u8 code)
>                 qca_wait_for_dump_collection(hdev);
>         }
>
> +       mutex_lock(&qca->hci_memdump_lock);
>         if (qca->memdump_state != QCA_MEMDUMP_COLLECTED) {
>                 bt_dev_err(hu->hdev, "clearing allocated memory due to memdump timeout");
> -               mutex_lock(&qca->hci_memdump_lock);
> -               if (qca_memdump)
> -                       memdump_buf = qca_memdump->memdump_buf_head;
> -               vfree(memdump_buf);
> -               kfree(qca_memdump);
> -               qca->qca_memdump = NULL;
> +               if (qca->qca_memdump) {
> +                       vfree(qca->qca_memdump->memdump_buf_head);
> +                       kfree(qca->qca_memdump);
> +                       qca->qca_memdump = NULL;
> +               }
>                 qca->memdump_state = QCA_MEMDUMP_TIMEOUT;
>                 cancel_delayed_work(&qca->ctrl_memdump_timeout);
> -               skb_queue_purge(&qca->rx_memdump_q);
> -               mutex_unlock(&qca->hci_memdump_lock);
> +       }
> +       mutex_unlock(&qca->hci_memdump_lock);
> +
> +       if (qca->memdump_state == QCA_MEMDUMP_TIMEOUT ||
> +           qca->memdump_state == QCA_MEMDUMP_COLLECTED) {
>                 cancel_work_sync(&qca->ctrl_memdump_evt);
> +               skb_queue_purge(&qca->rx_memdump_q);
>         }
>
>         clear_bit(QCA_HW_ERROR_EVENT, &qca->flags);
> --
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>