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)