On Thu, Aug 04, 2022 at 05:09:56PM +0200, Johan Hovold wrote:

The Qualcomm dwc3 runtime-PM implementation checks the xhci platform-device pointer in the wakeup-interrupt handler to determine whether the controller is in host mode and if so triggers a resume.

After a role switch in OTG mode the xhci platform-device would have been freed and the next wakeup from runtime suspend would access the freed memory.

Note that role switching is executed from a freezable workqueue, which guarantees that the pointer is stable during suspend.

Also note that runtime PM has been broken since commit 2664deb09306 ("usb: dwc3: qcom: Honor wakeup enabled/disabled state"), which incidentally also prevents this issue from being triggered.

Fixes: a4333c3a6ba9 ("usb: dwc3: Add Qualcomm DWC3 glue driver") Cc: stable@vger.kernel.org # 4.18 Signed-off-by: Johan Hovold johan+linaro@kernel.org

It'd be good to mention the introduction of dwc3_qcom_is_host() function. Initially I thought it is used in a single place, but going through the rest of the patches reveals that it is used later on.

Reviewed-by: Manivannan Sadhasivam manivannan.sadhasivam@linaro.org

Thanks, Mani

---

Changes in v2

• new patch

drivers/usb/dwc3/dwc3-qcom.c | 14 +++++++++++++- drivers/usb/dwc3/host.c | 1 + 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c index e9364141661b..6884026b9fad 100644 --- a/drivers/usb/dwc3/dwc3-qcom.c +++ b/drivers/usb/dwc3/dwc3-qcom.c @@ -298,6 +298,14 @@ static void dwc3_qcom_interconnect_exit(struct dwc3_qcom *qcom) icc_put(qcom->icc_path_apps); } +/* Only usable in contexts where the role can not change. */ +static bool dwc3_qcom_is_host(struct dwc3_qcom *qcom) +{

• struct dwc3 *dwc = platform_get_drvdata(qcom->dwc3);
• return dwc->xhci;

+}

static enum usb_device_speed dwc3_qcom_read_usb2_speed(struct dwc3_qcom *qcom) { struct dwc3 *dwc = platform_get_drvdata(qcom->dwc3); @@ -460,7 +468,11 @@ static irqreturn_t qcom_dwc3_resume_irq(int irq, void *data) if (qcom->pm_suspended) return IRQ_HANDLED;

• if (dwc->xhci)

• /*

• * This is safe as role switching is done from a freezable workqueue
  

• * and the wakeup interrupts are disabled as part of resume.
  

• */
  

• if (dwc3_qcom_is_host(qcom)) pm_runtime_resume(&dwc->xhci->dev);

return IRQ_HANDLED; diff --git a/drivers/usb/dwc3/host.c b/drivers/usb/dwc3/host.c index f56c30cf151e..f6f13e7f1ba1 100644 --- a/drivers/usb/dwc3/host.c +++ b/drivers/usb/dwc3/host.c @@ -135,4 +135,5 @@ int dwc3_host_init(struct dwc3 *dwc) void dwc3_host_exit(struct dwc3 *dwc) { platform_device_unregister(dwc->xhci);

• dwc->xhci = NULL;

}

2.35.1