Hi,
On Thu, Jun 4, 2020 at 6:59 AM Venkata Lakshmi Narayana Gubba
<gubbaven@xxxxxxxxxxxxxx> wrote:
>
> Due to race conditions between qca_hw_error and qca_controller_memdump
> during SSR timeout,the same pointer is freed twice. Which results to
> double free error. Now a lock is acquired while SSR state moved to timeout.
suggestion: Change "which results to double free error" to "This
results in a double free."
suggestion: Change "while SSR state moved to timeout" to "when SSR
state is changed to timeout"
>
> Signed-off-by: Venkata Lakshmi Narayana Gubba <gubbaven@xxxxxxxxxxxxxx>
> ---
> drivers/bluetooth/hci_qca.c | 19 ++++++++++++++-----
> 1 file changed, 14 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
> index 836949d..9110775 100644
> --- a/drivers/bluetooth/hci_qca.c
> +++ b/drivers/bluetooth/hci_qca.c
> @@ -983,8 +983,11 @@ 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;
> }
> @@ -1485,7 +1488,7 @@ 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;
> + struct qca_memdump_data *qca_memdump = NULL;
> char *memdump_buf = NULL;
>
> set_bit(QCA_HW_ERROR_EVENT, &qca->flags);
> @@ -1509,9 +1512,10 @@ 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);
> + qca_memdump = qca->qca_memdump;
> if (qca_memdump)
> memdump_buf = qca_memdump->memdump_buf_head;
> vfree(memdump_buf);
This section of code looks a bit unclear because it's only partially
in an if statement. Suggestion:
if (qca->qca_memdump) {
vfree(qca->qca_memdump->memdump_buf_head);
kfree(qca->qca_memdump);
qca->qca_memdump = NULL;
}
> @@ -1520,8 +1524,13 @@ static void qca_hw_error(struct hci_dev *hdev, u8 code)
> 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);
> }
Earlier in the function, you call qca_wait_for_dump_collection for
[Idle, Collecting] so the state should be either [Timeout, Collected]
at this branch. So, you can remove the `cancel_delayed_work` and
`skb_queue_purge` from above and just leave it only in the bottom
branch. Currently you're duplicating these calls unnecessarily.
I don't know if we discussed this in an earlier review but I noticed
that `qca_wait_for_dump_collection` doesn't actually pay attention to
the return value of `wait_on_bit_timeout`. I don't have context for
the order of calls anymore but is there a possibility for that timeout
to complete before `qca_memdump_timeout` is called? In that case, you
should probably set the state to timeout in
`qca_wait_for_dump_collection` as well.
>
> clear_bit(QCA_HW_ERROR_EVENT, &qca->flags);
> --
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
> of Code Aurora Forum, hosted by The Linux Foundation
>
