From 62c73bfea048e66168df09da6d3e4510ecda40bb Mon Sep 17 00:00:00 2001
From: Sven Peter <sven@svenpeter.dev>
Date: Mon, 28 Nov 2022 17:15:26 +0100
Subject: [PATCH] usb: dwc3: Fix race between dwc3_set_mode and __dwc3_set_mode
Git-commit: 62c73bfea048e66168df09da6d3e4510ecda40bb
References: git-fixes
Patch-mainline: v6.2-rc1

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.

Fixes: 41ce1456e1db ("usb: dwc3: core: make dwc3_set_mode() work properly")
Cc: stable <stable@kernel.org>
Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Signed-off-by: Sven Peter <sven@svenpeter.dev>
Link: https://lore.kernel.org/r/20221128161526.79730-1-sven@svenpeter.dev
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
 drivers/usb/dwc3/core.c |   17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -118,17 +118,22 @@ static void __dwc3_set_mode(struct work_
 	struct dwc3 *dwc = work_to_dwc(work);
 	unsigned long flags;
 	int ret;
+	u32 desired_dr_role;
 
-	if (!dwc->desired_dr_role)
+	spin_lock_irqsave(&dwc->lock, flags);
+	desired_dr_role = dwc->desired_dr_role;
+	spin_unlock_irqrestore(&dwc->lock, flags);
+
+	if (!desired_dr_role)
 		return;
 
-	if (dwc->desired_dr_role == dwc->current_dr_role)
+	if (desired_dr_role == dwc->current_dr_role)
 		return;
 
 	if (dwc->dr_mode != USB_DR_MODE_OTG)
 		return;
 
-	if (dwc->desired_dr_role == DWC3_GCTL_PRTCAP_OTG)
+	if (desired_dr_role == DWC3_GCTL_PRTCAP_OTG)
 		return;
 
 	switch (dwc->current_dr_role) {
@@ -145,13 +150,13 @@ static void __dwc3_set_mode(struct work_
 
 	spin_lock_irqsave(&dwc->lock, flags);
 
-	dwc3_set_prtcap(dwc, dwc->desired_dr_role);
+	dwc3_set_prtcap(dwc, desired_dr_role);
 
-	dwc->current_dr_role = dwc->desired_dr_role;
+	dwc->current_dr_role = 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)