linux-kernel - [PATCH] usb: dwc3: gadget: Fix null pointer dereference

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Date:   Wed,  4 May 2022 15:28:02 +0800
From:   Albert Wang <albertccwang@...gle.com>
To:     balbi@...nel.org, gregkh@...uxfoundation.org,
        quic_jackp@...cinc.com
Cc:     badhri@...gle.com, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, Albert Wang <albertccwang@...gle.com>
Subject: [PATCH] usb: dwc3: gadget: Fix null pointer dereference

There are still race conditions to hit the null pointer deference
with my previous commit. So I re-write the code to dereference the
pointer right after checking it is not null.

Fixes: 26288448120b ("usb: dwc3: gadget: Fix null pointer exception")

Signed-off-by: Albert Wang <albertccwang@...gle.com>
---
 drivers/usb/dwc3/gadget.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 19477f4bbf54..f2792968afd9 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -3366,15 +3366,14 @@ static bool dwc3_gadget_endpoint_trbs_complete(struct dwc3_ep *dep,
 	struct dwc3		*dwc = dep->dwc;
 	bool			no_started_trb = true;
 
-	if (!dep->endpoint.desc)
-		return no_started_trb;
-
 	dwc3_gadget_ep_cleanup_completed_requests(dep, event, status);
 
 	if (dep->flags & DWC3_EP_END_TRANSFER_PENDING)
 		goto out;
 
-	if (usb_endpoint_xfer_isoc(dep->endpoint.desc) &&
+	if (!dep->endpoint.desc)
+		return no_started_trb;
+	else if (usb_endpoint_xfer_isoc(dep->endpoint.desc) &&
 		list_empty(&dep->started_list) &&
 		(list_empty(&dep->pending_list) || status == -EXDEV))
 		dwc3_stop_active_transfer(dep, true, true);
-- 
2.36.0.464.gb9c8b46e94-goog