Re: [PATCH v3] usb: dwc3: qcom: check for hcd in dwc3_qcom_read_usb2_speed

[Peter Chen <peter.chen@oss.qualcomm.com>]

On 26-10-22 10:56:02, Prashanth K wrote:
> Currently dwc->xhci is not cleared if xhci_plat_probe() fails. During
> system suspend, dwc3_qcom_read_usb2_speed() checks dwc->xhci and assumes
> xhci is initialised. Since the probe failed, hcd will be null, and the
> subsequent access results in a NULL pointer dereference
> 
> Unable to handle kernel NULL pointer dereference at
> virtual address 0000000000000058
> 
> Call trace:
>   dwc3_qcom_pm_suspend
>   dpm_run_callback
>   device_suspend
>   dpm_suspend
>   dpm_suspend_start
>   suspend_devices_and_enter
>   pm_suspend
> 
> Explicitly check the hcd pointer in dwc3_qcom_read_usb2_speed
> before accessing it.
> 
> Fixes: 6895ea55c385 ("usb: dwc3: qcom: Configure wakeup interrupts during suspend")
> Signed-off-by: Prashanth K <prashanth.k@oss.qualcomm.com>

Reviewed-by: Peter Chen <peter.chen@oss.qualcomm.com>

Peter
> ---
> Changes in v3: 
>  - Initialised udev to null, as suggested by sashiko bot.
>  - Link to v2: https://lore.kernel.org/all/20261022044748.2303528-1-prashanth.k@oss.qualcomm.com/ 
> 
> Changes in v2:
>  - Added null pointer check in dwc3-qcom.c instead of marking xhci as null in host.c
>  - Link to v1: https://lore.kernel.org/all/20261014105711.1708244-1-prashanth.k@oss.qualcomm.com
> 
>  drivers/usb/dwc3/dwc3-qcom.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c
> index ac68b4218b56..e4bf0d5fc9f1 100644
> --- a/drivers/usb/dwc3/dwc3-qcom.c
> +++ b/drivers/usb/dwc3/dwc3-qcom.c
> @@ -231,7 +231,7 @@ static bool dwc3_qcom_is_host(struct dwc3_qcom *qcom)
>  
>  static enum usb_device_speed dwc3_qcom_read_usb2_speed(struct dwc3_qcom *qcom, int port_index)
>  {
> -	struct usb_device *udev;
> +	struct usb_device *udev = NULL;
>  	struct usb_hcd __maybe_unused *hcd;
>  	struct dwc3 *dwc = &qcom->dwc;
>  
> @@ -241,9 +241,8 @@ static enum usb_device_speed dwc3_qcom_read_usb2_speed(struct dwc3_qcom *qcom, i
>  	hcd = platform_get_drvdata(dwc->xhci);
>  
>  #ifdef CONFIG_USB
> -	udev = usb_hub_find_child(hcd->self.root_hub, port_index + 1);
> -#else
> -	udev = NULL;
> +	if (hcd)
> +		udev = usb_hub_find_child(hcd->self.root_hub, port_index + 1);
>  #endif
>  	if (!udev)
>  		return USB_SPEED_UNKNOWN;
> -- 
> 2.34.1
> 
> 

-- 

Thanks,
Peter Chen