linux-kernel - Re: [PATCH v2] usb: dwc3: core: Prevent USB core invalid event buffer address access

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Message-ID: <98e0cf35-f729-43e2-97f2-06120052a1cc@samsung.com>
Date: Sat, 10 Aug 2024 20:39:25 +0530
From: Selvarasu Ganesan <selvarasu.g@...sung.com>
To: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Cc: "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"jh0801.jung@...sung.com" <jh0801.jung@...sung.com>, "dh10.jung@...sung.com"
	<dh10.jung@...sung.com>, "naushad@...sung.com" <naushad@...sung.com>,
	"akash.m5@...sung.com" <akash.m5@...sung.com>, "rc93.raju@...sung.com"
	<rc93.raju@...sung.com>, "taehyun.cho@...sung.com"
	<taehyun.cho@...sung.com>, "hongpooh.kim@...sung.com"
	<hongpooh.kim@...sung.com>, "eomji.oh@...sung.com" <eomji.oh@...sung.com>,
	"shijie.cai@...sung.com" <shijie.cai@...sung.com>, "stable@...r.kernel.org"
	<stable@...r.kernel.org>
Subject: Re: [PATCH v2] usb: dwc3: core: Prevent USB core invalid event
 buffer address access


On 8/10/2024 4:58 AM, Thinh Nguyen wrote:
> On Thu, Aug 08, 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
> This is a workaround to your specific setup behavior. Please document in
> the commit message which platforms are impacted.
Please correct me if i am wrong. I dont think this workaround only 
applicable our specific setup. It could be a common issue across all 
other vendor platforms, and it's required to must check the controller 
status before clear the event buffers address.  What you think is it 
really required to mention the platform details in commit message?
>
>>          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.
>>
>> Cc: stable@...r.kernel.org
> We can keep the stable tag, but there's no issue with the commit below.


By mistaken I mentioned wrong commit ID. The correct commit id would be 
660e9bde74d69 ("usb: dwc3: remove num_event_buffers").
>
>> Fixes: 89d7f9629946 ("usb: dwc3: core: Skip setting event buffers for host only controllers")
>> Signed-off-by: Selvarasu Ganesan <selvarasu.g@...sung.com>
>> ---
>>
>> Changes in v2:
>> - Added separate check for USB controller status before cleaning the
>>    event buffer.
>> - Link to v1: https://urldefense.com/v3/__https://lore.kernel.org/lkml/20240722145617.537-1-selvarasu.g@samsung.com/__;!!A4F2R9G_pg!cvZmnaxTWtJKR4ZDRZDa-8mvxpvkf5KPx57IwSXTSEtEFIVkPullR7sTYP0AM9de0xFbHLKdM_5jzBUiBL3f9SuioYE$
>> ---
>>   drivers/usb/dwc3/core.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
>> index 734de2a8bd21..5b67d9bca71b 100644
>> --- a/drivers/usb/dwc3/core.c
>> +++ b/drivers/usb/dwc3/core.c
>> @@ -564,10 +564,15 @@ 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)
>>   		return;
>>   
> Please add comment here why we need this and which platform is impacted
> should we need to go back and test.

Do you want add comment as like below?. If yes, As i said earlier not 
required to mention our platform name as it could be a common issue 
across all the other vendor platforms.

/*Prevent USB controller invalid event buffer address access
in Exynos platform if USB controller still in active.*/
>
>> +	reg = dwc3_readl(dwc->regs, DWC3_DSTS);
>> +	if (!(reg & DWC3_DSTS_DEVCTRLHLT))
>> +		return;
>> +
>>   	evt = dwc->ev_buf;
>>   
>>   	evt->lpos = 0;
>> -- 
>> 2.17.1
>>
> Thanks,
> Thinh