[PATCH 5.15 709/731] usb: dwc3: Fix race between dwc3_set_mode and __dwc3_set_mode

Greg Kroah-Hartman
2022-12-28T16:02:09Z

From: Sven Peter <sven@svenpeter.dev>

commit 62c73bfea048e66168df09da6d3e4510ecda40bb upstream.

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>
---
drivers/usb/dwc3/core.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)

--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -120,21 +120,25 @@ static void __dwc3_set_mode(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) {
@@ -162,7 +166,7 @@ static void __dwc3_set_mode(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);
@@ -182,11 +186,11 @@ 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);

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) {