[PATCH v1] Bluetooth: hci_qca: Fix double free during SSR timeout

[PATCH v1] Bluetooth: hci_qca: Fix double free during SSR timeout

[Venkata Lakshmi Narayana Gubba]

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.

Signed-off-by: Venkata Lakshmi Narayana Gubba <gubbaven@codeaurora.org>
---
 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);
@@ -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);
 	}
 
 	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

Re: [PATCH v1] Bluetooth: hci_qca: Fix double free during SSR timeout

[bgodavar]

On 2020-06-04 19:27, Venkata Lakshmi Narayana Gubba 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.
> 
> Signed-off-by: Venkata Lakshmi Narayana Gubba <gubbaven@codeaurora.org>
> ---
>  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);
> @@ -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);
>  	}
> 
>  	clear_bit(QCA_HW_ERROR_EVENT, &qca->flags);

Reviewed-by: Balakrishna Godavarthi <bgodavar@codeaurora.org>

Re: [PATCH v1] Bluetooth: hci_qca: Fix double free during SSR timeout

[Abhishek Pandit-Subedi]

Hi,

On Thu, Jun 4, 2020 at 6:59 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. 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@codeaurora.org>
> ---
>  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
>

Re: [PATCH v1] Bluetooth: hci_qca: Fix double free during SSR timeout

[gubbaven]

Hi Abhishek,

On 2020-06-05 10:23, Abhishek Pandit-Subedi wrote:
> Hi,
> 
> On Thu, Jun 4, 2020 at 6:59 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. 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"
> 
[Venkata]:
Sure will update in next patchset.
>> 
>> Signed-off-by: Venkata Lakshmi Narayana Gubba 
>> <gubbaven@codeaurora.org>
>> ---
>>  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;
>   }
> 
[Venkata]:
Sure will update in next patchset.
>> @@ -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.
> 
[Venkata]:
I see only skb_queue_purge is getting duplicated and will update in next 
patchset.
But cancel_delayed_work is for qca->ctrl_memdump_timeout and 
cancel_work_sync is for
qca->ctrl_memdump_evt.So these calls are not getting duplicated.

If timeout happens in qca_wait_for_dump_collection, we are setting state 
to timeout
in subsequent if block which is  if (qca->memdump_state != 
QCA_MEMDUMP_COLLECTED).
>> 
>>         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
>> 

Regards,
Lakshmi Narayana.