linux-kernel - [PATCH] usb: dwc3: Skip TRBs while removing requests in disconnect path

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Message-Id: <1685562871-17024-1-git-send-email-quic_eserrao@quicinc.com>
Date:   Wed, 31 May 2023 12:54:31 -0700
From:   Elson Roy Serrao <quic_eserrao@...cinc.com>
To:     gregkh@...uxfoundation.org, Thinh.Nguyen@...opsys.com
Cc:     linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        quic_wcheng@...cinc.com, quic_jackp@...cinc.com,
        Elson Roy Serrao <quic_eserrao@...cinc.com>
Subject: [PATCH] usb: dwc3: Skip TRBs while removing requests in disconnect path

Consider a scenario where cable disconnect happens when there is an active
usb reqest queued to the UDC. As part of the disconnect we would issue an
end transfer with no interrupt-on-completion before giving back this
request. Since we are giving back the request without skipping TRBs the
num_trbs field of dwc3_request still holds the stale value previously used.
Function drivers re-use same request for a given bind-unbind session and
hence their dwc3_request context gets preserved across cable
disconnect/connect. When such a request gets re-queued after cable connect,
we would increase the num_trbs field on top of the previous stale value
thus incorrectly representing the number of TRBs used. Fix this by invoking
skip_trbs() in the ep disable path.

Signed-off-by: Elson Roy Serrao <quic_eserrao@...cinc.com>
---
 drivers/usb/dwc3/gadget.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 578804d..b45e917 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -986,6 +986,8 @@ static int __dwc3_gadget_ep_enable(struct dwc3_ep *dep, unsigned int action)
 	return 0;
 }

+static void dwc3_gadget_ep_skip_trbs(struct dwc3_ep *dep, struct dwc3_request *req);
+
 void dwc3_remove_requests(struct dwc3 *dwc, struct dwc3_ep *dep, int status)
 {
 	struct dwc3_request		*req;
@@ -1000,6 +1002,7 @@ void dwc3_remove_requests(struct dwc3 *dwc, struct dwc3_ep *dep, int status)
 	while (!list_empty(&dep->started_list)) {
 		req = next_request(&dep->started_list);

+		dwc3_gadget_ep_skip_trbs(dep, req);
 		dwc3_gadget_giveback(dep, req, status);
 	}

@@ -1012,6 +1015,7 @@ void dwc3_remove_requests(struct dwc3 *dwc, struct dwc3_ep *dep, int status)
 	while (!list_empty(&dep->cancelled_list)) {
 		req = next_request(&dep->cancelled_list);

+		dwc3_gadget_ep_skip_trbs(dep, req);
 		dwc3_gadget_giveback(dep, req, status);
 	}
 }
-- 
2.7.4