[PATCH] usb: dwc3: core: Prevent USB core invalid event buffer address access

[PATCH] usb: dwc3: core: Prevent USB core invalid event buffer address access

[Selvarasu Ganesan]

This commit addresses an issue where the USB core could access an
invalid event buffer address during runtime suspend, potentially causing
SMMU faults and other memory issues. The problem arises from the
following sequence.
	1. In dwc3_gadget_suspend, there is a chance of a timeout when
	moving the USB core to the halt state after clearing the
	run/stop bit by software.
	2. In dwc3_core_exit, the event buffer is cleared regardless of
	the USB core's status, which may lead to an SMMU faults and
	other memory issues. if the USB core tries to access the event
	buffer address.

To prevent this issue, this commit ensures that the event buffer address
is not cleared by software  when the USB core is active during runtime
suspend by checking its status before clearing the buffer address.

Signed-off-by: Selvarasu Ganesan <selvarasu.g@samsung.com>
---
 drivers/usb/dwc3/core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index cb82557678dd..c7c1a253862e 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -559,8 +559,10 @@ int dwc3_event_buffers_setup(struct dwc3 *dwc)
 void dwc3_event_buffers_cleanup(struct dwc3 *dwc)
 {
 	struct dwc3_event_buffer	*evt;
+	u32				reg;
 
-	if (!dwc->ev_buf)
+	reg = dwc3_readl(dwc->regs, DWC3_DSTS);
+	if (!dwc->ev_buf || !(reg & DWC3_DSTS_DEVCTRLHLT))
 		return;
 
 	evt = dwc->ev_buf;
-- 
2.17.1

Re: [PATCH] usb: dwc3: core: Prevent USB core invalid event buffer address access

[Thinh Nguyen]

On Mon, Jul 22, 2024, Selvarasu Ganesan wrote:
> This commit addresses an issue where the USB core could access an
> invalid event buffer address during runtime suspend, potentially causing
> SMMU faults and other memory issues. The problem arises from the
> following sequence.
> 	1. In dwc3_gadget_suspend, there is a chance of a timeout when
> 	moving the USB core to the halt state after clearing the
> 	run/stop bit by software.
> 	2. In dwc3_core_exit, the event buffer is cleared regardless of
> 	the USB core's status, which may lead to an SMMU faults and
> 	other memory issues. if the USB core tries to access the event
> 	buffer address.
> 
> To prevent this issue, this commit ensures that the event buffer address
> is not cleared by software  when the USB core is active during runtime
> suspend by checking its status before clearing the buffer address.

What happen after adding this check? Can the device resume and function
properly afterward? If not, do you know if a soft-reset will recover the
issue?

Thanks,
Thinh

> 
> Signed-off-by: Selvarasu Ganesan <selvarasu.g@samsung.com>
> ---
>  drivers/usb/dwc3/core.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index cb82557678dd..c7c1a253862e 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -559,8 +559,10 @@ int dwc3_event_buffers_setup(struct dwc3 *dwc)
>  void dwc3_event_buffers_cleanup(struct dwc3 *dwc)
>  {
>  	struct dwc3_event_buffer	*evt;
> +	u32				reg;
>  
> -	if (!dwc->ev_buf)
> +	reg = dwc3_readl(dwc->regs, DWC3_DSTS);
> +	if (!dwc->ev_buf || !(reg & DWC3_DSTS_DEVCTRLHLT))
>  		return;
>  
>  	evt = dwc->ev_buf;
> -- 
> 2.17.1
> 

Re: [PATCH] usb: dwc3: core: Prevent USB core invalid event buffer address access

[Selvarasu Ganesan]

On 8/7/2024 5:44 AM, Thinh Nguyen wrote:
> On Mon, Jul 22, 2024, Selvarasu Ganesan wrote:
>> This commit addresses an issue where the USB core could access an
>> invalid event buffer address during runtime suspend, potentially causing
>> SMMU faults and other memory issues. The problem arises from the
>> following sequence.
>> 	1. In dwc3_gadget_suspend, there is a chance of a timeout when
>> 	moving the USB core to the halt state after clearing the
>> 	run/stop bit by software.
>> 	2. In dwc3_core_exit, the event buffer is cleared regardless of
>> 	the USB core's status, which may lead to an SMMU faults and
>> 	other memory issues. if the USB core tries to access the event
>> 	buffer address.
>>
>> To prevent this issue, this commit ensures that the event buffer address
>> is not cleared by software  when the USB core is active during runtime
>> suspend by checking its status before clearing the buffer address.
> What happen after adding this check? Can the device resume and function
> properly afterward? If not, do you know if a soft-reset will recover the
> issue?
>
> Thanks,
> Thinh

Yes, we can see the proper resume with this fix even if the USB IP core 
not entered into halted during suspend.

And we not tried soft reset as this fix is working fine.

Anyway soft reset is part of resume sequence and it will reset or 
recover the USB IP state machine.


Thanks,

Selva

>
>> Signed-off-by: Selvarasu Ganesan <selvarasu.g@samsung.com>
>> ---
>>   drivers/usb/dwc3/core.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
>> index cb82557678dd..c7c1a253862e 100644
>> --- a/drivers/usb/dwc3/core.c
>> +++ b/drivers/usb/dwc3/core.c
>> @@ -559,8 +559,10 @@ int dwc3_event_buffers_setup(struct dwc3 *dwc)
>>   void dwc3_event_buffers_cleanup(struct dwc3 *dwc)
>>   {
>>   	struct dwc3_event_buffer	*evt;
>> +	u32				reg;
>>   
>> -	if (!dwc->ev_buf)
>> +	reg = dwc3_readl(dwc->regs, DWC3_DSTS);
>> +	if (!dwc->ev_buf || !(reg & DWC3_DSTS_DEVCTRLHLT))
>>   		return;
>>   
>>   	evt = dwc->ev_buf;
>> -- 
>> 2.17.1

Re: [PATCH] usb: dwc3: core: Prevent USB core invalid event buffer address access

[Thinh Nguyen]

On Wed, Aug 07, 2024, Selvarasu Ganesan wrote:
> 
> On 8/7/2024 5:44 AM, Thinh Nguyen wrote:
> > On Mon, Jul 22, 2024, Selvarasu Ganesan wrote:
> >> This commit addresses an issue where the USB core could access an
> >> invalid event buffer address during runtime suspend, potentially causing
> >> SMMU faults and other memory issues. The problem arises from the
> >> following sequence.
> >> 	1. In dwc3_gadget_suspend, there is a chance of a timeout when
> >> 	moving the USB core to the halt state after clearing the
> >> 	run/stop bit by software.
> >> 	2. In dwc3_core_exit, the event buffer is cleared regardless of
> >> 	the USB core's status, which may lead to an SMMU faults and
> >> 	other memory issues. if the USB core tries to access the event
> >> 	buffer address.
> >>
> >> To prevent this issue, this commit ensures that the event buffer address
> >> is not cleared by software  when the USB core is active during runtime
> >> suspend by checking its status before clearing the buffer address.
> > What happen after adding this check? Can the device resume and function
> > properly afterward? If not, do you know if a soft-reset will recover the
> > issue?
> >
> > Thanks,
> > Thinh
> 
> Yes, we can see the proper resume with this fix even if the USB IP core 
> not entered into halted during suspend.
> 
> And we not tried soft reset as this fix is working fine.
> 
> Anyway soft reset is part of resume sequence and it will reset or 
> recover the USB IP state machine.
> 

Ok.

Just wonder, what condition does the buffer access become invalid?
While it makes sense that we should not cleanup the buffer while the
controller is in run state, I don't think SMMU fault will always occur
when (!(reg & DWC3_DSTS_DEVCTRLHLT)) right?

> 
> Thanks,
> 
> Selva
> 
> >
> >> Signed-off-by: Selvarasu Ganesan <selvarasu.g@samsung.com>
> >> ---
> >>   drivers/usb/dwc3/core.c | 4 +++-
> >>   1 file changed, 3 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> >> index cb82557678dd..c7c1a253862e 100644
> >> --- a/drivers/usb/dwc3/core.c
> >> +++ b/drivers/usb/dwc3/core.c
> >> @@ -559,8 +559,10 @@ int dwc3_event_buffers_setup(struct dwc3 *dwc)
> >>   void dwc3_event_buffers_cleanup(struct dwc3 *dwc)
> >>   {
> >>   	struct dwc3_event_buffer	*evt;
> >> +	u32				reg;
> >>   
> >> -	if (!dwc->ev_buf)
> >> +	reg = dwc3_readl(dwc->regs, DWC3_DSTS);
> >> +	if (!dwc->ev_buf || !(reg & DWC3_DSTS_DEVCTRLHLT))
> >>   		return;

Can you separate the checks so we don't have to read register for all
conditions?

if (!dwc->ev_buf)
	return;

/*
 * If dwc3_core_exit() fails, event buffer is not
 * accessible for <XYZ> platforms.
 */
reg = dwc3_readl(dwc->regs, DWC3_DSTS);
if (!(reg & DWC3_DSTS_DEVCTRLHLT))
	return;

Thanks,
Thinh

> >>   
> >>   	evt = dwc->ev_buf;
> >> -- 
> >> 2.17.1

Re: [PATCH] usb: dwc3: core: Prevent USB core invalid event buffer address access

[Selvarasu Ganesan]

On 8/8/2024 5:51 AM, Thinh Nguyen wrote:
> On Wed, Aug 07, 2024, Selvarasu Ganesan wrote:
>> On 8/7/2024 5:44 AM, Thinh Nguyen wrote:
>>> On Mon, Jul 22, 2024, Selvarasu Ganesan wrote:
>>>> This commit addresses an issue where the USB core could access an
>>>> invalid event buffer address during runtime suspend, potentially causing
>>>> SMMU faults and other memory issues. The problem arises from the
>>>> following sequence.
>>>> 	1. In dwc3_gadget_suspend, there is a chance of a timeout when
>>>> 	moving the USB core to the halt state after clearing the
>>>> 	run/stop bit by software.
>>>> 	2. In dwc3_core_exit, the event buffer is cleared regardless of
>>>> 	the USB core's status, which may lead to an SMMU faults and
>>>> 	other memory issues. if the USB core tries to access the event
>>>> 	buffer address.
>>>>
>>>> To prevent this issue, this commit ensures that the event buffer address
>>>> is not cleared by software  when the USB core is active during runtime
>>>> suspend by checking its status before clearing the buffer address.
>>> What happen after adding this check? Can the device resume and function
>>> properly afterward? If not, do you know if a soft-reset will recover the
>>> issue?
>>>
>>> Thanks,
>>> Thinh
>> Yes, we can see the proper resume with this fix even if the USB IP core
>> not entered into halted during suspend.
>>
>> And we not tried soft reset as this fix is working fine.
>>
>> Anyway soft reset is part of resume sequence and it will reset or
>> recover the USB IP state machine.
>>
> Ok.
>
> Just wonder, what condition does the buffer access become invalid?

Its very hard to conclude the condition here as this issue is happening 
in some random scenario when do connect/disconnect USB cable 
continuously to Host PC with some time interval by using test scripts.

> While it makes sense that we should not cleanup the buffer while the
> controller is in run state, I don't think SMMU fault will always occur
> when (!(reg & DWC3_DSTS_DEVCTRLHLT)) right?

Yes are correct. We are not always getting SMMU fault.
>
>> Thanks,
>>
>> Selva
>>
>>>> Signed-off-by: Selvarasu Ganesan <selvarasu.g@samsung.com>
>>>> ---
>>>>    drivers/usb/dwc3/core.c | 4 +++-
>>>>    1 file changed, 3 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
>>>> index cb82557678dd..c7c1a253862e 100644
>>>> --- a/drivers/usb/dwc3/core.c
>>>> +++ b/drivers/usb/dwc3/core.c
>>>> @@ -559,8 +559,10 @@ int dwc3_event_buffers_setup(struct dwc3 *dwc)
>>>>    void dwc3_event_buffers_cleanup(struct dwc3 *dwc)
>>>>    {
>>>>    	struct dwc3_event_buffer	*evt;
>>>> +	u32				reg;
>>>>    
>>>> -	if (!dwc->ev_buf)
>>>> +	reg = dwc3_readl(dwc->regs, DWC3_DSTS);
>>>> +	if (!dwc->ev_buf || !(reg & DWC3_DSTS_DEVCTRLHLT))
>>>>    		return;
> Can you separate the checks so we don't have to read register for all
> conditions?


Sure, will update in next version.

>
> if (!dwc->ev_buf)
> 	return;
>
> /*
>   * If dwc3_core_exit() fails, event buffer is not
>   * accessible for <XYZ> platforms.
>   */
> reg = dwc3_readl(dwc->regs, DWC3_DSTS);
> if (!(reg & DWC3_DSTS_DEVCTRLHLT))
> 	return;
>
> Thanks,
> Thinh
>
>>>>    
>>>>    	evt = dwc->ev_buf;
>>>> -- 
>>>> 2.17.1