[PATCH 18/19] usb: isp1760: wait for the TT clear in endpoint_disable

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Josef Bacik <josef@toxicpanda.com>

The driver sets qh->tt_buffer_dirty and calls usb_hub_clear_tt_buffer()
when a transfer to a full or low speed device fails or is unlinked while
it is running. The hub driver stores urb->ep in its list and
hub_tt_work() hands it back to isp1760_clear_tt_buffer_complete() after
the CLEAR_TT_BUFFER request to the hub.

Nothing keeps the endpoint until then. isp1760_endpoint_disable() frees
the QH at once. If the device is unplugged, the unlink of a running URB
queues such a request, and usb_disconnect() goes on to free the
usb_device and its configurations, which hold the struct
usb_host_endpoint. The callback then reads ep->hcpriv from freed memory
and, if it is not NULL, writes to whatever it points to. A change of the
configuration or altsetting only frees the QH, under a callback which
has loaded ep->hcpriv without the lock.

The HCD has to wait, like ehci_endpoint_disable(),
xhci_endpoint_disable() and fotg210_endpoint_disable() do. hub_tt_work()
calls the callback for every entry, also if the request failed, and
hub_quiesce() flushes the work, so the wait ends.

Fixes: 74ad60292bf0 ("usb/isp1760: Clear TT buffer on interrupted low & full speed transfers")
Cc: stable <stable@kernel.org>
Cc: Rui Miguel Silva <rui.silva@linaro.org>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/usb/isp1760/isp1760-hcd.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/usb/isp1760/isp1760-hcd.c b/drivers/usb/isp1760/isp1760-hcd.c
index 6c52c6f59d69..3cbf5fe3ed34 100644
--- a/drivers/usb/isp1760/isp1760-hcd.c
+++ b/drivers/usb/isp1760/isp1760-hcd.c
@@ -2071,12 +2071,23 @@ static void isp1760_endpoint_disable(struct usb_hcd *hcd,
 	struct isp1760_qh *qh, *qh_iter;
 	int i;
 
+rescan:
 	spin_lock_irqsave(&priv->lock, spinflags);
 
 	qh = ep->hcpriv;
 	if (!qh)
 		goto out;
 
+	/*
+	 * The hub driver still has a pointer to the endpoint. Wait until it
+	 * has called isp1760_clear_tt_buffer_complete().
+	 */
+	if (qh->tt_buffer_dirty) {
+		spin_unlock_irqrestore(&priv->lock, spinflags);
+		schedule_timeout_uninterruptible(1);
+		goto rescan;
+	}
+
 	WARN_ON(!list_empty(&qh->qtd_list));
 
 	for (i = 0; i < QH_END; i++)

-- 
2.56.0