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 <[email protected]>
---
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
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 <[email protected]>
> ---
> 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 <[email protected]>
Thanks!
Thinh