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* [PATCH] usb: dwc3: Fix race between dwc3_set_mode and __dwc3_set_mode
@ 2022-11-28 16:15 Sven Peter
  2022-11-28 19:14 ` Thinh Nguyen
  0 siblings, 1 reply; 2+ messages in thread
From: Sven Peter @ 2022-11-28 16:15 UTC (permalink / raw)
  To: Thinh Nguyen, Greg Kroah-Hartman
  Cc: Sven Peter, Felipe Balbi, Janne Grunau, linux-usb, linux-kernel, asahi

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")
Signed-off-by: Sven Peter <sven@svenpeter.dev>
---
 drivers/usb/dwc3/core.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 1f348bc867c2..fc38a8b13efa 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -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) {
-- 
2.25.1


^ permalink raw reply related	[flat|nested] 2+ messages in thread
* Re: [PATCH] usb: dwc3: Fix race between dwc3_set_mode and __dwc3_set_mode
  2022-11-28 16:15 [PATCH] usb: dwc3: Fix race between dwc3_set_mode and __dwc3_set_mode Sven Peter
@ 2022-11-28 19:14 ` Thinh Nguyen
  0 siblings, 0 replies; 2+ messages in thread
From: Thinh Nguyen @ 2022-11-28 19:14 UTC (permalink / raw)
  To: Sven Peter
  Cc: Thinh Nguyen, Greg Kroah-Hartman, Felipe Balbi, Janne Grunau,
	linux-usb, stable, linux-kernel, asahi

Hi,

On Mon, Nov 28, 2022, Sven Peter wrote:
> 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")
> Signed-off-by: Sven Peter <sven@svenpeter.dev>
> ---
>  drivers/usb/dwc3/core.c | 16 ++++++++++------
>  1 file changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 1f348bc867c2..fc38a8b13efa 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -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) {
> -- 
> 2.25.1
> 

This looks good to me. This should also go on stable.

Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>

Thanks!
Thinh

^ permalink raw reply	[flat|nested] 2+ messages in thread
end of thread, other threads:[~2022-11-28 19:15 UTC | newest]

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2022-11-28 16:15 [PATCH] usb: dwc3: Fix race between dwc3_set_mode and __dwc3_set_mode Sven Peter
2022-11-28 19:14 ` Thinh Nguyen

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