[kernel PATCH v1 0/1] Clear workqueue to avoid use-after-free

[kernel PATCH v1 0/1] Clear workqueue to avoid use-after-free

[Zhengping Jiang]

After the hci_sync rework, cmd_sync_work was cleared when calling
hci_unregister_dev, but not when powering off the adapter.
Use-after-free errors happened because a work is still scheduled
when cmd is freed by __mgmt_power_off.

Changes in v1:
- Clear cmd_sync_work queue before clearing the mgmt cmd list

Zhengping Jiang (1):
  Bluetooth: hci_sync: clear workqueue before clear mgmt cmd

 net/bluetooth/hci_sync.c | 2 ++
 1 file changed, 2 insertions(+)

-- 
2.39.2.637.g21b0678d19-goog

[kernel PATCH v1 1/1] Bluetooth: hci_sync: clear workqueue before clear mgmt cmd

[Zhengping Jiang]

Clear cmd_sync_work queue before clearing the mgmt cmd list to avoid
racing conditions which cause use-after-free.

When powering off the adapter, the mgmt cmd list will be cleared. If a
work is queued in the cmd_sync_work queue at the same time, it will
cause the risk of use-after-free, as the cmd pointer is not checked
before use.

Signed-off-by: Zhengping Jiang <jiangzp@google.com>
---

Changes in v1:
- Clear cmd_sync_work queue before clearing the mgmt cmd list

 net/bluetooth/hci_sync.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index 117eedb6f709..6609434e3125 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -4840,6 +4840,8 @@ int hci_dev_close_sync(struct hci_dev *hdev)
 
 	auto_off = hci_dev_test_and_clear_flag(hdev, HCI_AUTO_OFF);
 
+	hci_cmd_sync_clear(hdev);
+
 	if (!auto_off && hdev->dev_type == HCI_PRIMARY &&
 	    !hci_dev_test_flag(hdev, HCI_USER_CHANNEL) &&
 	    hci_dev_test_flag(hdev, HCI_MGMT))
-- 
2.39.2.637.g21b0678d19-goog

Re: [kernel PATCH v1 1/1] Bluetooth: hci_sync: clear workqueue before clear mgmt cmd

[Zhengping Jiang]

Hi,

We need to revise this patch after a local test failure. I will update
after finding the cause.

Thanks,
Zhengping

On Tue, Feb 21, 2023 at 4:09 PM Zhengping Jiang <jiangzp@google.com> wrote:
>
> Clear cmd_sync_work queue before clearing the mgmt cmd list to avoid
> racing conditions which cause use-after-free.
>
> When powering off the adapter, the mgmt cmd list will be cleared. If a
> work is queued in the cmd_sync_work queue at the same time, it will
> cause the risk of use-after-free, as the cmd pointer is not checked
> before use.
>
> Signed-off-by: Zhengping Jiang <jiangzp@google.com>
> ---
>
> Changes in v1:
> - Clear cmd_sync_work queue before clearing the mgmt cmd list
>
>  net/bluetooth/hci_sync.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
> index 117eedb6f709..6609434e3125 100644
> --- a/net/bluetooth/hci_sync.c
> +++ b/net/bluetooth/hci_sync.c
> @@ -4840,6 +4840,8 @@ int hci_dev_close_sync(struct hci_dev *hdev)
>
>         auto_off = hci_dev_test_and_clear_flag(hdev, HCI_AUTO_OFF);
>
> +       hci_cmd_sync_clear(hdev);
> +
>         if (!auto_off && hdev->dev_type == HCI_PRIMARY &&
>             !hci_dev_test_flag(hdev, HCI_USER_CHANNEL) &&
>             hci_dev_test_flag(hdev, HCI_MGMT))
> --
> 2.39.2.637.g21b0678d19-goog
>