FAILED: patch "[PATCH] usb: dwc3: Fix race between dwc3_set_mode and __dwc3_set_mode" failed to apply to 5.4-stable tree

The patch below does not apply to the 5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

Possible dependencies:

62c73bfea048 ("usb: dwc3: Fix race between dwc3_set_mode and __dwc3_set_mode") 07903626d988 ("usb: dwc3: core: Do not perform GCTL_CORE_SOFTRESET during bootup") afbd04e66e5d ("usb: dwc3: core: Deprecate GCTL.CORESOFTRESET") f88359e1588b ("usb: dwc3: core: Do core softreset when switch mode") f580170f135a ("usb: dwc3: Add splitdisable quirk for Hisilicon Kirin Soc") dc336b19e82d ("usb: dwc3: core: do not queue work if dr_mode is not USB_DR_MODE_OTG") c2cd3452d5f8 ("usb: dwc3: support continuous runtime PM with dual role")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 62c73bfea048e66168df09da6d3e4510ecda40bb Mon Sep 17 00:00:00 2001
From: Sven Peter <[email protected]>
Date: Mon, 28 Nov 2022 17:15:26 +0100
Subject: [PATCH] usb: dwc3: Fix race between dwc3_set_mode and __dwc3_set_mode

dwc->desired_dr_role is changed by dwc3_set_mode inside a spinlock but then read by __dwc3_set_mode outside of that lock. This can lead to a race condition when very quick successive role switch events happen:

CPU A

	dwc3_set_mode(DWC3_GCTL_PRTCAP_HOST) // first role switch event
		spin_lock_irqsave(&dwc->lock, flags);
		dwc->desired_dr_role = mode; // DWC3_GCTL_PRTCAP_HOST
		spin_unlock_irqrestore(&dwc->lock, flags);
		queue_work(system_freezable_wq, &dwc->drd_work);

CPU B

	__dwc3_set_mode
		// ....
		spin_lock_irqsave(&dwc->lock, flags);
		// desired_dr_role is DWC3_GCTL_PRTCAP_HOST
		dwc3_set_prtcap(dwc, dwc->desired_dr_role);
		spin_unlock_irqrestore(&dwc->lock, flags);

CPU A

	dwc3_set_mode(DWC3_GCTL_PRTCAP_DEVICE) // second event
		spin_lock_irqsave(&dwc->lock, flags);
		dwc->desired_dr_role = mode; // DWC3_GCTL_PRTCAP_DEVICE
		spin_unlock_irqrestore(&dwc->lock, flags);

CPU B (continues running __dwc3_set_mode)

	switch (dwc->desired_dr_role) { // DWC3_GCTL_PRTCAP_DEVICE
	// ....
	case DWC3_GCTL_PRTCAP_DEVICE:
		// ....
		ret = dwc3_gadget_init(dwc);

We then have DWC3_GCTL.DWC3_GCTL_PRTCAPDIR = DWC3_GCTL_PRTCAP_HOST and dwc->current_dr_role = DWC3_GCTL_PRTCAP_HOST but initialized the controller in device mode. It's also possible to get into a state where both host and device are intialized at the same time. Fix this race by creating a local copy of desired_dr_role inside __dwc3_set_mode while holding dwc->lock.

index 1f348bc867c2..fc38a8b13efa 100644
@@ -122,21 +122,25 @@ static void __dwc3_set_mode(struct work_struct *work)
 	unsigned long flags;
 	int ret;
 	u32 reg;
+	u32 desired_dr_role;
 
 	mutex_lock(&dwc->mutex);
+	spin_lock_irqsave(&dwc->lock, flags);
+	desired_dr_role = dwc->desired_dr_role;
+	spin_unlock_irqrestore(&dwc->lock, flags);
 
 	pm_runtime_get_sync(dwc->dev);
 
 	if (dwc->current_dr_role == DWC3_GCTL_PRTCAP_OTG)
 		dwc3_otg_update(dwc, 0);
 
-	if (!dwc->desired_dr_role)
+	if (!desired_dr_role)
 		goto out;
 
-	if (dwc->desired_dr_role == dwc->current_dr_role)
+	if (desired_dr_role == dwc->current_dr_role)
 		goto out;
 
-	if (dwc->desired_dr_role == DWC3_GCTL_PRTCAP_OTG && dwc->edev)
+	if (desired_dr_role == DWC3_GCTL_PRTCAP_OTG && dwc->edev)
 		goto out;
 
 	switch (dwc->current_dr_role) {

@@ -164,7 +168,7 @@ static void __dwc3_set_mode(struct work_struct *work)
 	 */
 	if (dwc->current_dr_role && ((DWC3_IP_IS(DWC3) ||
 			DWC3_VER_IS_PRIOR(DWC31, 190A)) &&
-			dwc->desired_dr_role != DWC3_GCTL_PRTCAP_OTG)) {
+			desired_dr_role != DWC3_GCTL_PRTCAP_OTG)) {
 		reg = dwc3_readl(dwc->regs, DWC3_GCTL);
 		reg |= DWC3_GCTL_CORESOFTRESET;
 		dwc3_writel(dwc->regs, DWC3_GCTL, reg);

@@ -184,11 +188,11 @@ static void __dwc3_set_mode(struct work_struct *work)
 
 	spin_lock_irqsave(&dwc->lock, flags);
 
-	dwc3_set_prtcap(dwc, dwc->desired_dr_role);
+	dwc3_set_prtcap(dwc, desired_dr_role);
 
 	spin_unlock_irqrestore(&dwc->lock, flags);
 
-	switch (dwc->desired_dr_role) {
+	switch (desired_dr_role) {
 	case DWC3_GCTL_PRTCAP_HOST:
 		ret = dwc3_host_init(dwc);
 		if (ret) {