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.

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>

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 1f348bc867c22afa68da07e1a81419f97a7cdb57..fc38a8b13efa6eb95294074b53b29bea064516fa 100644 (file)
--- 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) {