linux-kernel - [PATCH] xhci: guard accesses to ep_state in xhci_endpoint

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Date:   Tue, 31 Aug 2021 17:02:59 +0100
From:   Phil Elwell <phil@...pberrypi.com>
To:     Mathias Nyman <mathias.nyman@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jonathan Bell <jonathan@...pberrypi.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] xhci: guard accesses to ep_state in xhci_endpoint_reset()

From: Jonathan Bell <jonathan@...pberrypi.com>

See https://github.com/raspberrypi/linux/issues/3981

Two read-modify-write cycles on ep->ep_state are not guarded by
xhci->lock. Fix these.

Signed-off-by: Jonathan Bell <jonathan@...pberrypi.com>
---
 drivers/usb/host/xhci.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index f3dabd02382c2..902f410874e8e 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -3213,10 +3213,13 @@ static void xhci_endpoint_reset(struct usb_hcd *hcd,
 		return;
 
 	/* Bail out if toggle is already being cleared by a endpoint reset */
+	spin_lock_irqsave(&xhci->lock, flags);
 	if (ep->ep_state & EP_HARD_CLEAR_TOGGLE) {
 		ep->ep_state &= ~EP_HARD_CLEAR_TOGGLE;
+		spin_unlock_irqrestore(&xhci->lock, flags);
 		return;
 	}
+	spin_unlock_irqrestore(&xhci->lock, flags);
 	/* Only interrupt and bulk ep's use data toggle, USB2 spec 5.5.4-> */
 	if (usb_endpoint_xfer_control(&host_ep->desc) ||
 	    usb_endpoint_xfer_isoc(&host_ep->desc))
@@ -3302,8 +3305,10 @@ static void xhci_endpoint_reset(struct usb_hcd *hcd,
 	xhci_free_command(xhci, cfg_cmd);
 cleanup:
 	xhci_free_command(xhci, stop_cmd);
+	spin_lock_irqsave(&xhci->lock, flags);
 	if (ep->ep_state & EP_SOFT_CLEAR_TOGGLE)
 		ep->ep_state &= ~EP_SOFT_CLEAR_TOGGLE;
+	spin_unlock_irqrestore(&xhci->lock, flags);
 }
 
 static int xhci_check_streams_endpoint(struct xhci_hcd *xhci,
-- 
2.25.1