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From:   Johan Hovold <johan+linaro@kernel.org>
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Felipe Balbi <balbi@kernel.org>
Cc:     Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Andy Gross <agross@kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
        Konrad Dybcio <konrad.dybcio@somainline.org>,
        Krishna Kurapati <quic_kriskura@quicinc.com>,
        Stephen Boyd <swboyd@chromium.org>,
        Doug Anderson <dianders@chromium.org>,
        "Matthias Kaehlcke" <mka@chromium.org>,
        Pavankumar Kondeti <quic_pkondeti@quicinc.com>,
        quic_ppratap@quicinc.com, quic_vpulyala@quicinc.com,
        linux-arm-msm@vger.kernel.org, linux-usb@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        Johan Hovold <johan+linaro@kernel.org>, stable@vger.kernel.org
Subject: [PATCH v2 4/9] usb: dwc3: qcom: fix use-after-free on runtime-PM wakeup
Date:   Thu,  4 Aug 2022 17:09:56 +0200
Message-Id: <20220804151001.23612-5-johan+linaro@kernel.org>
In-Reply-To: <20220804151001.23612-1-johan+linaro@kernel.org>
References: <20220804151001.23612-1-johan+linaro@kernel.org>
MIME-Version: 1.0
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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>
---

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