On 09/04/2022 15:58, Duoming Zhou wrote:
> There is a potential UAF bug in nfcmrvl usb driver between
> unregister and resume operation.
>
> The race that cause that UAF can be shown as below:
>
> (FREE) | (USE)
> | nfcmrvl_resume
> | nfcmrvl_submit_bulk_urb
> | nfcmrvl_bulk_complete
> | nfcmrvl_nci_recv_frame
> | nfcmrvl_fw_dnld_recv_frame
> | skb_queue_tail
> nfcmrvl_disconnect |
> nfcmrvl_nci_unregister_dev |
> nfcmrvl_fw_dnld_deinit | ...
> destroy_workqueue //(1) |
> ... | queue_work //(2)
>
> When nfcmrvl usb driver is resuming, we detach the device.
> The workqueue is destroyed in position (1), but it will be
> latter used in position (2), which leads to data race.
I miss here something. How can you queue work on a destroyed workqueue?
When workqueue is destroyed, no more work should be executed. Unless you
mean the case that draining the work (during destroying, not after)
causes the (2) to happen?
> This patch reorders the nfcmrvl_fw_dnld_deinit after
> nci_unregister_device in order to prevent UAF. Because
> nci_unregister_device will not return until finish all
> operations from upper layer.
>
> Signed-off-by: Duoming Zhou <[email protected]>
> ---
> drivers/nfc/nfcmrvl/main.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/nfc/nfcmrvl/main.c b/drivers/nfc/nfcmrvl/main.c
> index 2fcf545012b..5ed17b23ee8 100644
> --- a/drivers/nfc/nfcmrvl/main.c
> +++ b/drivers/nfc/nfcmrvl/main.c
> @@ -186,12 +186,11 @@ void nfcmrvl_nci_unregister_dev(struct nfcmrvl_private *priv)
> if (priv->ndev->nfc_dev->fw_download_in_progress)
> nfcmrvl_fw_dnld_abort(priv);
>
> - nfcmrvl_fw_dnld_deinit(priv);
> -
> if (gpio_is_valid(priv->config.reset_n_io))
> gpio_free(priv->config.reset_n_io);
>
> nci_unregister_device(ndev);
> + nfcmrvl_fw_dnld_deinit(priv);
The new order matches reverse-probe, so actually makes sense.
> nci_free_device(ndev);
> kfree(priv);
> }
Best regards,
Krzysztof
Hello,
I am sorry for the delay.
On Sat, 9 Apr 2022 17:10:05 +0200 Krzysztof Kozlowski wrote:
> > There is a potential UAF bug in nfcmrvl usb driver between
> > unregister and resume operation.
> >
> > The race that cause that UAF can be shown as below:
> >
> > (FREE) | (USE)
> > | nfcmrvl_resume
> > | nfcmrvl_submit_bulk_urb
> > | nfcmrvl_bulk_complete
> > | nfcmrvl_nci_recv_frame
> > | nfcmrvl_fw_dnld_recv_frame
> > | skb_queue_tail
> > nfcmrvl_disconnect |
> > nfcmrvl_nci_unregister_dev |
> > nfcmrvl_fw_dnld_deinit | ...
> > destroy_workqueue //(1) |
> > ... | queue_work //(2)
> >
> > When nfcmrvl usb driver is resuming, we detach the device.
> > The workqueue is destroyed in position (1), but it will be
> > latter used in position (2), which leads to data race.
>
> I miss here something. How can you queue work on a destroyed workqueue?
> When workqueue is destroyed, no more work should be executed. Unless you
> mean the case that draining the work (during destroying, not after)
> causes the (2) to happen?
Sorry, I make a mistake in my patch. The destroy_workqueue() will not
return until all work is finished. So the UAF bug is not exist.
Actually, there is a double free bug in nfcmrvl_nci_unregister_dev(). The root
cause is shown below:
(FREE) | (USE)
| nfcmrvl_resume
| nfcmrvl_submit_bulk_urb
| nfcmrvl_bulk_complete
| nfcmrvl_nci_recv_frame
| nfcmrvl_fw_dnld_recv_frame
| queue_work
| fw_dnld_rx_work
| fw_dnld_over
| release_firmware
| kfree(fw); //(1)
nfcmrvl_disconnect |
nfcmrvl_nci_unregister_dev |
nfcmrvl_fw_dnld_abort |
fw_dnld_over | ...
if (priv->fw_dnld.fw) |
release_firmware |
kfree(fw); //(2) |
... | fw = NULL;
When nfcmrvl usb driver is resuming, we detach the device.
The release_firmware() will deallocate firmware in position (1),
but firmware will be deallocate again in position (2), which
leads to double free.
> > This patch reorders the nfcmrvl_fw_dnld_deinit after
> > nci_unregister_device in order to prevent UAF. Because
> > nci_unregister_device will not return until finish all
> > operations from upper layer.
> >
> > Signed-off-by: Duoming Zhou <[email protected]>
> > ---
> > drivers/nfc/nfcmrvl/main.c | 3 +--
> > 1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/drivers/nfc/nfcmrvl/main.c b/drivers/nfc/nfcmrvl/main.c
> > index 2fcf545012b..5ed17b23ee8 100644
> > --- a/drivers/nfc/nfcmrvl/main.c
> > +++ b/drivers/nfc/nfcmrvl/main.c
> > @@ -186,12 +186,11 @@ void nfcmrvl_nci_unregister_dev(struct nfcmrvl_private *priv)
> > if (priv->ndev->nfc_dev->fw_download_in_progress)
> > nfcmrvl_fw_dnld_abort(priv);
> >
> > - nfcmrvl_fw_dnld_deinit(priv);
> > -
> > if (gpio_is_valid(priv->config.reset_n_io))
> > gpio_free(priv->config.reset_n_io);
> >
> > nci_unregister_device(ndev);
> > + nfcmrvl_fw_dnld_deinit(priv);
>
> The new order matches reverse-probe, so actually makes sense.
>
> > nci_free_device(ndev);
> > kfree(priv);
> > }
I will send "[PATCH] drivers: nfc: nfcmrvl: fix double free bug in
nfcmrvl_nci_unregister_dev()" as soon as possible.
Best regards,
Duoming Zhou
On 10/04/2022 10:30, [email protected] wrote:
(...)
>
> (FREE) | (USE)
> | nfcmrvl_resume
> | nfcmrvl_submit_bulk_urb
> | nfcmrvl_bulk_complete
> | nfcmrvl_nci_recv_frame
> | nfcmrvl_fw_dnld_recv_frame
> | queue_work
> | fw_dnld_rx_work
> | fw_dnld_over
> | release_firmware
> | kfree(fw); //(1)
> nfcmrvl_disconnect |
> nfcmrvl_nci_unregister_dev |
> nfcmrvl_fw_dnld_abort |
> fw_dnld_over | ...
> if (priv->fw_dnld.fw) |
> release_firmware |
> kfree(fw); //(2) |
> ... | fw = NULL;
>
> When nfcmrvl usb driver is resuming, we detach the device.
> The release_firmware() will deallocate firmware in position (1),
> but firmware will be deallocate again in position (2), which
> leads to double free.
Indeed. The code looks racy. It uses the fw_download_in_progress
variable which in core is partially protected with device_lock(). Moving
code around might not solve the issue entirely because there is no
synchronization here.
>
>>> This patch reorders the nfcmrvl_fw_dnld_deinit after
>>> nci_unregister_device in order to prevent UAF. Because
>>> nci_unregister_device will not return until finish all
>>> operations from upper layer.
>>>
>>> Signed-off-by: Duoming Zhou <[email protected]>
>>> ---
>>> drivers/nfc/nfcmrvl/main.c | 3 +--
>>> 1 file changed, 1 insertion(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/nfc/nfcmrvl/main.c b/drivers/nfc/nfcmrvl/main.c
>>> index 2fcf545012b..5ed17b23ee8 100644
>>> --- a/drivers/nfc/nfcmrvl/main.c
>>> +++ b/drivers/nfc/nfcmrvl/main.c
>>> @@ -186,12 +186,11 @@ void nfcmrvl_nci_unregister_dev(struct nfcmrvl_private *priv)
>>> if (priv->ndev->nfc_dev->fw_download_in_progress)
>>> nfcmrvl_fw_dnld_abort(priv);
>>>
>>> - nfcmrvl_fw_dnld_deinit(priv);
>>> -
>>> if (gpio_is_valid(priv->config.reset_n_io))
>>> gpio_free(priv->config.reset_n_io);
>>>
>>> nci_unregister_device(ndev);
>>> + nfcmrvl_fw_dnld_deinit(priv);
>>
>> The new order matches reverse-probe, so actually makes sense.
>>
>>> nci_free_device(ndev);
>>> kfree(priv);
>>> }
>
> I will send "[PATCH] drivers: nfc: nfcmrvl: fix double free bug in
> nfcmrvl_nci_unregister_dev()" as soon as possible.
Thanks!
Best regards,
Krzysztof