linux-kernel - usb: xhci: Don't change the status of stalled TDs on failed Stop EP

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Message-ID: <20250310093934.7d688648@foxbook>
Date: Mon, 10 Mar 2025 09:39:34 +0100
From: Michal Pecio <michal.pecio@...il.com>
To: Mathias Nyman <mathias.nyman@...el.com>, Greg Kroah-Hartman
 <gregkh@...uxfoundation.org>
Cc: linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: usb: xhci: Don't change the status of stalled TDs on failed Stop EP

When the device stalls an endpoint, current TD is assigned -EPIPE
status and Reset Endpoint is queued. If a Stop Endpoint is pending
at the time, it will run before Reset Endpoint and fail due to the
stall. Its handler will change TD's status to -EPROTO before Reset
Endpoint handler runs and initiates giveback.

Check if the stall has already been handled and don't try to do it
again. Since xhci_handle_halted_endpoint() performs this check too,
not overwriting td->status is the only difference.

I haven't seen this case yet, but I have seen a related one where
the xHC has already executed Reset Endpoint, EP Context state is
now Stopped and EP_HALTED is set. If the xHC took a bit longer to
execute Reset Endpoint, said case would become this one.

Signed-off-by: Michal Pecio <michal.pecio@...il.com>
---
 drivers/usb/host/xhci-ring.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 9e4940220252..28ebc0fc5bc2 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -1215,7 +1215,14 @@ static void xhci_handle_cmd_stop_ep(struct xhci_hcd *xhci, int slot_id,
 	 */
 		switch (GET_EP_CTX_STATE(ep_ctx)) {
 		case EP_STATE_HALTED:
-			xhci_dbg(xhci, "Stop ep completion raced with stall, reset ep\n");
+			xhci_dbg(xhci, "Stop ep completion raced with stall\n");
+			/*
+			 * If the halt happened before Stop Endpoint failed, its transfer event
+			 * should have already been handled and Reset Endpoint should be pending.
+			 */
+			if (ep->ep_state & EP_HALTED)
+				goto reset_done;
+
 			if (ep->ep_state & EP_HAS_STREAMS) {
 				reset_type = EP_SOFT_RESET;
 			} else {
@@ -1226,8 +1233,11 @@ static void xhci_handle_cmd_stop_ep(struct xhci_hcd *xhci, int slot_id,
 			}
 			/* reset ep, reset handler cleans up cancelled tds */
 			err = xhci_handle_halted_endpoint(xhci, ep, td, reset_type);
+			xhci_dbg(xhci, "Stop ep completion resetting ep, status %d\n", err);
 			if (err)
 				break;
+reset_done:
+			/* Reset EP handler will clean up cancelled TDs */
 			ep->ep_state &= ~EP_STOP_CMD_PENDING;
 			return;
 		case EP_STATE_STOPPED:
-- 
2.48.1