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

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Message-ID: <20251114002946.427ab4xdq7qhbi2k@synopsys.com>
Date: Fri, 14 Nov 2025 00:29:47 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: Manish Nagar <manish.nagar@....qualcomm.com>
CC: Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        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

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