linux-kernel - Re: [PATCH] usb: dwc3: Fix race condition between concurrent dwc3_remove

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Message-ID: <CADGrZwUnwv5m5r-Vv8CxwiHSxOw3HDfBQJRWezPQRJ_c6V8rXg@mail.gmail.com>
Date: Wed, 19 Nov 2025 22:34:11 +0530
From: Manish Nagar <manish.nagar@....qualcomm.com>
To: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: dwc3: Fix race condition between concurrent
 dwc3_remove_requests() call paths

Hi Greg,

I can’t identify a specific commit ID that I’m confident was the patch
introducing the bug.But I found the race condition and suggested this
patch to fix it.

Regards,

Manish


On 11/14/2025 5:59 AM, Thinh Nguyen wrote:
> On Thu, Nov 13, 2025, Manish Nagar wrote:
>> Hi ,
>>
>> Thanks for the suggestion ,
>>
>> On above your suggestion, I added a check for  dep->number as
>>
>> if ((req->status == DWC3_REQUEST_STATUS_COMPLETED) && (dep->number > 1))
>> return;
>>
>> I included this condition to prevent enumeration failures. During the sequence
>> dwc3_gadget_giveback → dwc3_ep0_interrupt → dwc3_thread_interrupt, the giveback
>> for ep0 does not complete, so this check ensures proper handling.
>>
>> Please share your feedback, and I will proceed with v2 accordingly.
>>
> No, add checks for ep0 too.
>
> Try this:
>
> diff --git a/drivers/usb/dwc3/ep0.c b/drivers/usb/dwc3/ep0.c
> index b4229aa13f37..e0bad5708664 100644
> --- a/drivers/usb/dwc3/ep0.c
> +++ b/drivers/usb/dwc3/ep0.c
> @@ -94,6 +94,7 @@ static int __dwc3_gadget_ep0_queue(struct dwc3_ep *dep,
>       req->request.actual     = 0;
>       req->request.status     = -EINPROGRESS;
>       req->epnum              = dep->number;
> +     req->status             = DWC3_REQUEST_STATUS_QUEUED;
>
>       list_add_tail(&req->list, &dep->pending_list);
>
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 1f67fb6aead5..a1d2ff9254b4 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -228,6 +228,13 @@ void dwc3_gadget_giveback(struct dwc3_ep *dep, struct dwc3_request *req,
>   {
>       struct dwc3                     *dwc = dep->dwc;
>
> +     /*
> +      * The request might have been processed and completed while the
> +      * spinlock was released. Skip processing if already completed.
> +      */
> +     if (req->status == DWC3_REQUEST_STATUS_COMPLETED)
> +             return;
> +
>       dwc3_gadget_del_and_unmap_request(dep, req, status);
>       req->status = DWC3_REQUEST_STATUS_COMPLETED;
>
> ---
>
> BR,
> Thinh