[PATCH stable-4.19 2/4] usb: dwc3: qcom: fix use-after-free on runtime-PM wakeup

[Johan Hovold <johan@kernel.org>]

From: Johan Hovold <johan+linaro@kernel.org>

commit  a872ab303d5ddd4c965f9cd868677781a33ce35a upstream.

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
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://lore.kernel.org/r/20220804151001.23612-5-johan+linaro@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ johan: adjust context for 5.4 ]
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 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 5bb5384f3612..9d5320562e81 100644
--- a/drivers/usb/dwc3/dwc3-qcom.c
+++ b/drivers/usb/dwc3/dwc3-qcom.c
@@ -173,6 +173,14 @@ static int dwc3_qcom_register_extcon(struct dwc3_qcom *qcom)
 	return 0;
 }
 
+/* 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 void dwc3_qcom_disable_interrupts(struct dwc3_qcom *qcom)
 {
 	if (qcom->hs_phy_irq) {
@@ -280,7 +288,11 @@ 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 1a3878a3be78..124e9f80dccd 100644
--- a/drivers/usb/dwc3/host.c
+++ b/drivers/usb/dwc3/host.c
@@ -142,4 +142,5 @@ void dwc3_host_exit(struct dwc3 *dwc)
 	phy_remove_lookup(dwc->usb3_generic_phy, "usb3-phy",
 			  dev_name(dwc->dev));
 	platform_device_unregister(dwc->xhci);
+	dwc->xhci = NULL;
 }
-- 
2.35.1